Update restic version to 0.8.1 (#257)

Author: tamalsaha

docs/setup/install.md

@@ -110,6 +110,6 @@ GitTag = 0.5.1
 CommitTimestamp = 2017-10-10T05:24:23
 
 $ kubectl exec -it $POD_NAME -c operator -n $POD_NAMESPACE restic version
-restic 0.8.0
+restic 0.8.1
 compiled with go1.9 on linux/amd64
 ```

hack/docker/setup.sh

@@ -14,7 +14,7 @@ source "$REPO_ROOT/hack/libbuild/common/public_image.sh"
 
 APPSCODE_ENV=${APPSCODE_ENV:-dev}
 IMG=stash
-RESTIC_VER=${RESTIC_VER:-0.8.0}
+RESTIC_VER=${RESTIC_VER:-0.8.1}
 RESTIC_BRANCH=${RESTIC_BRANCH:-stash-0.4.2}
 
 DIST=$REPO_ROOT/dist