GFS2: Skip check for mandatory locks when unlocking

gfs2_lock() will skip locks on file which have mode set to 02666. This is a problem in cases where the mode of the file is changed after a process has obtained a lock on the file. Such a lock will be skipped and will result in a BUG in locks_remove_flock().

gfs2_lock() should skip the check for mandatory locks when unlocking a file.

Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>