common: add _disable_dmesg_check function

Introduce _disable_dmesg_check function, which can be called by tests
that generate WARNINGs etc. on purpose, so the tests won't fail
_dmesg_check.

Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

common/rc

@@ -2805,6 +2805,12 @@ _get_device_size()
 	grep `_short_dev $1` /proc/partitions | awk '{print $3}'
 }
 
+# don't check dmesg log after test
+_disable_dmesg_check()
+{
+	rm -f ${RESULT_DIR}/check_dmesg
+}
+
 init_rc()
 {
 	if [ "$iam" == new ]