[SPARK-27178][K8S][BRANCH-2.4] adding nss package to fix tests

## What changes were proposed in this pull request?

see also:  apache#24111

while performing some tests on our existing minikube and k8s infrastructure, i noticed that the integration tests were failing. i dug in and discovered the following message buried at the end of the stacktrace:

```
  Caused by: java.io.FileNotFoundException: /usr/lib/libnss3.so
  	at sun.security.pkcs11.Secmod.initialize(Secmod.java:193)
  	at sun.security.pkcs11.SunPKCS11.<init>(SunPKCS11.java:218)
  	... 81 more
```
after i added the `nss` package to `resource-managers/kubernetes/docker/src/main/dockerfiles/spark/Dockerfile`, everything worked.

this is also impacting current builds.  see:  https://amplab.cs.berkeley.edu/jenkins/job/testing-k8s-prb-make-spark-distribution-unified/8959/console

## How was this patch tested?

i tested locally before pushing, and the build system will test the rest.

Closes apache#24137 from shaneknapp/add-nss-package.

Authored-by: shane knapp <[email protected]>
Signed-off-by: Marcelo Vanzin <[email protected]>

Author: shaneknapp

resource-managers/kubernetes/docker/src/main/dockerfiles/spark/Dockerfile

@@ -30,7 +30,7 @@ ARG k8s_tests=kubernetes/tests
 
 RUN set -ex && \
     apk upgrade --no-cache && \
-    apk add --no-cache bash tini libc6-compat linux-pam && \
+    apk add --no-cache bash tini libc6-compat linux-pam nss && \
     mkdir -p /opt/spark && \
     mkdir -p /opt/spark/work-dir && \
     touch /opt/spark/RELEASE && \