ocfs2_dlm: Fixes race between migrate and dirty

dlmthread was removing lockres' from the dirty list
and resetting the dirty flag before shuffling the list.
This patch retains the dirty state flag until the lists
are shuffled.

Signed-off-by: Kurt Hackel <kurt.hackel@oracle.com>
Signed-off-by: Sunil Mushran <Sunil.Mushran@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>