Have run-tests monitor sync before crashing

There have been a few failures where output is generated just before we
crash but it didn't have a chance to be written.  Add a best-effort
background sync before crashing.  There's a good chance it'll hang if
the system is stuck so we don't wait for it directly, just for .. some
time to pass.

Signed-off-by: Zach Brown <zab@versity.com>

tests/run-tests.sh

@@ -505,7 +505,10 @@ crash_monitor()
 		fi
 
 		if [ "$bad" != 0 ]; then
-			echo "run-tests monitor triggering crash"
+			echo "run-tests monitor syncing and triggering crash"
+			# hail mary, the sync could well hang
+			(echo s > /proc/sysrq-trigger) &
+			sleep 5
 			echo c > /proc/sysrq-trigger
 			exit 1
 		fi