LU-9795 mdt: only set groups if GID is not squashed

LU-9795 mdt: only set groups if GID is not squashed

In new_init_ucred(), only set groups for local client if GID is
not squashed. Otherwise, GID squashing would be by-passed.

Test-Parameters: testlist=sanity-sec envdefinitions=ONLY="17 18 19 20 21 22",SHARED_KEY=true
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I56961c62a93d99e6a62c72cca7b4fa6e9b3388b9
Reviewed-on: https://review.whamcloud.com/33316
Tested-by: Jenkins
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>