ocfs2: Remove overzealous BUG_ON during blocked lock processing

During blocked lock processing, we should consider the possibility that the
lock is no longer blocking.

Joel Becker <joel.becker@oracle.com> assisted in fixing this issue.

Reported-by: David Teigland <teigland@redhat.com>
Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>