wmcore-dev image has file permission issues during Jenkins tests

[d-ylee]

Impact of the bug
This bug affects the Jenkins CI/CD, as when it happens, the Jenkins job does not finish to completion.

Describe the bug
Occasionally, we encounter a file permission error when running unit tests or pylint in our wmcore-dev image. This would cause the job to completely stop. In our image, we have to set the user and group to the home directory to our node user. Occassionally, the permissions are not set in time for the script to run. The error usually occurs when we are trying to set up our rucio config file in the env_unittests.sh script.

How to reproduce it
Steps to reproduce the behavior:

1. Submit a PR that triggers the Jenkins CI

Expected behavior
For file permission error to not occur

Additional context and error message

+ echo 'Testing slice 9 of 12 for build 203'
Testing slice 9 of 12 for build 203
+ docker compose -f /build/cmsbld/jenkins/workspace/WMCore-Unittest-Baseline/WMCore-Test-Base/docker-compose.yml exec -u 501 -e BUILD_ID=203 -e SLICES=12 -e SLICE=9 wmcore-unittests /home/cmsbld/TestScripts/test-wmcorepy3.sh
~ ~
Sourcing a python3 unittest environment
/home/cmsbld/TestScripts/env_unittest.sh: line 55: /home/cmsbld/etc/rucio.cfg: Permission denied
script returned exit code 1

Proposed solution
A possible solution would be to re-order some lines in the entrypoint script. We could first assign the home directory to the test user, then pull scripts in as the user.

Updates to this will be made in dmwm/CMSKubernetes.