LU-5641 tests: ensure user daemon is in group bin on mds

LU-5641 tests: ensure user daemon is in group bin on mds

The previous fix for this problem only fixed groups on client.
That worked as long as we were only testing with el7 client,
but was an incomplete solution for el7 client/servers.
Need to apply the same fix to mds too to keep things consistent.

Signed-off-by: Bob Gossman <bob.glossman@intel.com>
Change-Id: I411970c591a72b0393ed892f15da1f5d6340df8c
Reviewed-on: http://review.whamcloud.com/12762
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Minh Diep <minh.diep@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>