staging/lustre/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.
Signed-off-by: Patrick Farrell <paf@cray.com>
Reviewed-on: http://review.whamcloud.com/12459
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5817Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: frank zago <fzago@cray.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/llite/file.c

@@ -1553,6 +1553,11 @@ ll_get_grouplock(struct inode *inode, struct file *file, unsigned long arg)
 	struct ccc_grouplock    grouplock;
 	int		     rc;
 
+	if (arg == 0) {
+		CWARN("group id for group lock must not be 0\n");
+		return -EINVAL;
+	}
+
 	if (ll_file_nolock(file))
 		return -EOPNOTSUPP;