GFS2: gfs2_logd should be using interruptible waits

Looks like this crept in, in a recent update.

Reported-by:  Krzysztof Urbaniak <urban@bash.org.pl>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index cde1248..ac750bd 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -932,7 +932,7 @@
 
 		do {
 			prepare_to_wait(&sdp->sd_logd_waitq, &wait,
-					TASK_UNINTERRUPTIBLE);
+					TASK_INTERRUPTIBLE);
 			if (!gfs2_ail_flush_reqd(sdp) &&
 			    !gfs2_jrnl_flush_reqd(sdp) &&
 			    !kthread_should_stop())