Move back to realtime clock

On some systems MONOTONIC still causes a hang.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/gettime.c b/gettime.c
index b1431f3..c0d27e4 100644
--- a/gettime.c
+++ b/gettime.c
@@ -130,7 +130,7 @@
 	} else {
 		struct timespec ts;
 
-		if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0) {
+		if (clock_gettime(CLOCK_REALTIME, &ts) < 0) {
 			clock_gettime_works = 0;
 			goto gtod;
 		}