t554[01]-http-push: refactor, add non-ff tests

Move non-fast forward tests to lib-httpd.sh so that we don't have to
duplicate the tests in both t5540 and t5541.

Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/t/t5540-http-push.sh b/t/t5540-http-push.sh
index bb18f8b..37fe875 100755
--- a/t/t5540-http-push.sh
+++ b/t/t5540-http-push.sh
@@ -137,6 +137,9 @@
 
 '
 
+test_http_push_nonff "$HTTPD_DOCUMENT_ROOT_PATH"/test_repo.git \
+	"$ROOT_PATH"/test_repo_clone master
+
 stop_httpd
 
 test_done