always set sidecar bucket access check env variable

[Sneha-at]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind api-change
/kind bug
/kind cleanup
/kind design
/kind documentation

/kind failing-test

/kind feature
/kind flake

What this PR does / why we need it:
#1053 added a check where the env variable for enable_sidecar_bucket_access_check is set only if a. the driver is unmanaged b. the sidecar version is supported for managed driver. While the environment variable is conditionally set we always try to fetch the value for the env variable TEST_WITH_SIDECAR_BUCKET_ACCESS_CHECK during tests this was causing fatal errors in the testsuite. I have now updated the logic to always set the env variable irrespective of driver version.
Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:
Verified the test run is triggered correctly

make e2e-test E2E_TEST_USE_GKE_MANAGED_DRIVER=true E2E_TEST_BUILD_DRIVER=false BUILD_GCSFUSE_FROM_SOURCE=false  
PROJECT is snehaaradhey-gke-dev
CLUSTER_LOCATION is us-central1-c
CLUSTER_NAME is test-gcsfuse
OVERLAY is stable
STAGINGVERSION is v1.20.0-52-g02af95be
DRIVER_IMAGE is gcr.io/gke-release/gcs-fuse-csi-driver
SIDECAR_IMAGE is gcr.io/gke-release/gcs-fuse-csi-driver-sidecar-mounter
WEBHOOK_IMAGE is gcr.io/gke-release/gcs-fuse-csi-driver-webhook
./test/e2e/run-e2e-local.sh
.........

  
Running Suite: Cloud Storage FUSE CSI Driver - /usr/local/google/home/snehaaradhey/go/src/GoogleCloudPlatform/gcs-fuse-csi-driver/test/e2e
==========================================================================================================================================
Random Seed: 1763080338 - will randomize all specs

Will run 346 of 458 specs
Running in parallel across 10 processes
SSSS
------------------------------
S [SKIPPED] [7.711 seconds]
E2E Test Suite [Driver: gcsfuse.csi.storage.gke.io HNS] [Testpattern: CSI Ephemeral-volume (default fs)] gcsfuseIntegration [It] should succeed in buffered_read test 1
/usr/local/google/home/snehaaradhey/go/src/GoogleCloudPlatform/gcs-fuse-csi-driver/test/e2e/testsuites/gcsfuse_integration.go:733

  Timeline >>
  STEP: Creating a kubernetes client @ 11/14/25 00:32:25.722
  I1114 00:32:25.722189 505127 util.go:453] >>> kubeConfig: /usr/local/google/home/snehaaradhey/.kube/config
  STEP: Building a namespace api object, basename gcsfuse-integration @ 11/14/25 00:32:25.735
  STEP: Waiting for a default service account to be provisioned in namespace @ 11/14/25 00:32:26.052
  STEP: Waiting for kube-root-ca.crt to be provisioned in namespace @ 11/14/25 00:32:26.142
  I1114 00:32:26.261280 505127 specs.go:740] Creating Kubernetes Service Account gcsfuse-csi-sa
  I1114 00:32:26.335386 505127 volume_resource.go:128] Creating resource for CSI ephemeral inline volume
  STEP: Creating bucket "fd40fef6-349a-4b6a-b59b-d66e92cba6ff" @ 11/14/25 00:32:26.337
  STEP: Checking GCSFuse version and skip test if needed @ 11/14/25 00:32:27.893
  I1114 00:32:27.960348 505127 specs.go:180] Creating Pod 
  I1114 00:32:33.282071 505127 specs.go:747] Deleting Kubernetes Service Account gcsfuse-csi-sa
  STEP: Destroying namespace "gcsfuse-integration-2517" for this suite. @ 11/14/25 00:32:33.358
  << Timeline

  [SKIPPED] skip gcsfuse integration test buffered_read for gcsfuse version 3.2.0-gke.0
  In [It] at: /usr/local/google/home/snehaaradhey/go/src/GoogleCloudPlatform/gcs-fuse-csi-driver/test/e2e/testsuites/gcsfuse_integration.go:201 @ 11/14/25 00:32:32.7
------------------------------
• [9.535 seconds]
E2E Test Suite [Driver: gcsfuse.csi.storage.gke.io] [Testpattern: CSI Ephemeral-volume (default fs)] volumes should store data in implicit directory
/usr/local/google/home/snehaaradhey/go/src/GoogleCloudPlatform/gcs-fuse-csi-driver/test/e2e/testsuites/volumes.go:297

  Timeline >>
  STEP: Creating a kubernetes client @ 11/14/25 00:32:25.744
  I1114 00:32:25.744563 505145 util.go:453] >>> kubeConfig: /usr/local/google/home/snehaaradhey/.kube/config
  STEP: Building a namespace api object, basename volumes @ 11/14/25 00:32:25.758
  STEP: Waiting for a default service account to be provisioned in namespace @ 11/14/25 00:32:26.15
  STEP: Waiting for kube-root-ca.crt to be provisioned in namespace @ 11/14/25 00:32:26.229
  I1114 00:32:26.347487 505145 specs.go:740] Creating Kubernetes Service Account gcsfuse-csi-sa
  I1114 00:32:26.420844 505145 volume_resource.go:128] Creating resource for CSI ephemeral inline volume
.........

Does this PR introduce a user-facing change?:

NONE