Add missing couchbase password mount to oxauth key rotation manifest

[moabu]

INFO - certmanager - 2020-09-16 00:01:35,283 - Processing updates for service oxauth
Traceback (most recent call last):
  File "/app/scripts/entrypoint.py", line 82, in <module>
    cli(prog_name="certmanager")
  File "/usr/lib/python3.8/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python3.8/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3.8/site-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python3.8/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3.8/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/app/scripts/entrypoint.py", line 78, in patch
    callback_cls(manager, dry_run, **_opts).patch()
  File "/app/scripts/oxauth_handler.py", line 185, in __init__
    password = get_couchbase_password(manager)
  File "/src/pygluu-containerlib/pygluu/containerlib/persistence/couchbase.py", line 50, in get_couchbase_password
    with open(password_file) as f:
FileNotFoundError: [Errno 2] No such file or directory: '/etc/gluu/conf/couchbase_password'