Fix URL schemes in dokku urls output

Previously, the presence of TLS certificates would cause `dokku urls` to
output all https URLs, even for domains which were not configured to use
TLS.

This change introduces a URLS file in the app's directory which contains
the URLs with schemes based on whether they have been configured to use
TLS in the nginx config.

Signed-off-by: Lewis Marshall <lewis@lmars.net>

tests/unit/test_helper.bash

@@ -92,6 +92,10 @@ destroy_app() {
   echo $TEST_APP | dokku apps:destroy $TEST_APP
 }
 
+add_domain() {
+  dokku domains:add $TEST_APP $1
+}
+
 deploy_app() {
   APP_TYPE="$1"; APP_TYPE=${APP_TYPE:="nodejs-express"}
   TMP=$(mktemp -d -t "$TARGET.XXXXX")