test: make entrypoint script behavior configurable
test: make entrypoint script behavior configurable

Adds cli parsing to the entrypoint script allowing for:
1. Custom path to micro-osd script
   This allows easier testing of the script itself or quick
   and dirty customization for special one-off tests
2. Selecting tests to run (or "ALL" or "NONE")
   This allows the user to run only a subset of the tests as needed.
3. Option to pause indefinitely after tests complete
   This keeps the containerized environment alive after tests
   have run for debugging or just for creating a quick and dirty
   ceph environment for playing around.

Signed-off-by: John Mulligan <eda8ad33169deab44f9fe65847f99e368da6c91b@redhat.com>

ceph/go-ceph,ceph/go-ceph,ceph/go-ceph