GFS2: remove iopen glocks from cache on failed deletes

GFS2: remove iopen glocks from cache on failed deletes

When a file gets deleted on GFS2, if a node can't get an exclusive lock on the
file's iopen glock, it punts on actually freeing up the space, because another
node is using the file.  When it does this, it needs to drop the iopen glock
from its cache so that the other node can get an exclusive lock on it. Now,
gfs2_delete_inode() sets GL_NOCACHE before dropping the shared lock on the
iopen glock in preparation for grabbing it in the exclusive state.  Since the
node needs the glock in the exclusive state, dropping the shared lock from the
cache doesn't slow down the case where no other nodes are using the file.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>