LU-5817 clio: Do not allow group locks with gid 0

LU-5817 clio: Do not allow group locks with gid 0

When a group lock with GID=0 is released (put_grouplock is
called), an assertion in cl_put_grouplock is hit.

We should not allow group lock requests with GID=0, instead
we should return -EINVAL.

Also fix random_group_id so it never returns gid==0.

Change-Id: I56e58791742809da5353a4d8dfbf3b80a22f3814
Signed-off-by: Patrick Farrell <paf@cray.com>
Reviewed-on: http://review.whamcloud.com/12459
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: frank zago <fzago@cray.com>