DLM: Reanimate CF_WRITE_PENDING flag

CF_WRITE_PENDING flag has been reanimated to make dlm_send stop properly
when running dlm_lowcomms_stop.

Signed-off-by: Tadashi Miyauchi <miyauchi@toshiba-tops.co.jp>
Signed-off-by: Tsutomu Owa <tsutomu.owa@toshiba.co.jp>
Signed-off-by: David Teigland <teigland@redhat.com>