[SPARK-23680] Fix entrypoint.sh to properly support Arbitrary UIDs

## What changes were proposed in this pull request?

As described in SPARK-23680, entrypoint.sh returns an error code because of a command pipeline execution where it is expected in case of Openshift environments, where arbitrary UIDs are used to run containers

## How was this patch tested?

This patch was manually tested by using docker-image-toll.sh script to generate a Spark driver image and running an example against an OpenShift cluster.

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Ricardo Martinelli de Oliveira <rmartine@rmartine.gru.redhat.com>

Closes apache#20822 from rimolive/rmartine-spark-23680.

resource-managers/kubernetes/docker/src/main/dockerfiles/spark/entrypoint.sh

@@ -22,7 +22,10 @@ set -ex
 # Check whether there is a passwd entry for the container UID
 myuid=$(id -u)
 mygid=$(id -g)
+# turn off -e for getent because it will return error code in anonymous uid case
+set +e
 uidentry=$(getent passwd $myuid)
+set -e
 
 # If there is no passwd entry for the container UID, attempt to create one
 if [ -z "$uidentry" ] ; then