ocfs2/dlm: dlm_thread should not sleep while holding the dlm_spinlock

This patch addresses the bug in which the dlm_thread could go to sleep
while holding the dlm_spinlock.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>