dlm: fix slow rsb search in dir recovery

The function used to find an rsb during directory
recovery was searching the single linear list of
rsb's.  This wasted a lot of time compared to
using the standard hash table to find the rsb.

Signed-off-by: David Teigland <teigland@redhat.com>

diff --cc fs/dlm/dir.c
Simple merge

diff --cc fs/dlm/lock.c
Simple merge

diff --cc fs/dlm/lock.h
Simple merge