common: Check fs consistency on TEST_DEV only when needed

Currently we're checking file system consistency on TEST_DEV after every
successful test run even though the TEST_DEV might not even be used in
that test.

Fix it by introducing _require_test to for the test ti indicate that
it's about to use TEST_DEV.

Also add _require_test to the new script so that this requirement is a
default.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

check

@@ -625,7 +625,8 @@ for section in $HOST_OPTIONS_SECTIONS; do
 	    then
 		try="$try $seqnum"
 		n_try=`expr $n_try + 1`
-		_check_test_fs
+		test -f ${RESULT_DIR}/require_test && _check_test_fs
+		rm -f ${RESULT_DIR}/require_test
 		test -f ${RESULT_DIR}/require_scratch && _check_scratch_fs
 		rm -f ${RESULT_DIR}/require_scratch
 	    fi