Fix for git < v1.7.5

This change should be compatible with all git version.
(get-url available from v1.7.5)

update.sh

@@ -893,7 +893,7 @@ done
 # git remote set-url origin https://github.com/mailcow/mailcow-dockerized
 
 DEFAULT_REPO=https://github.com/mailcow/mailcow-dockerized
-CURRENT_REPO=$(git remote get-url origin)
+CURRENT_REPO=$(git config --get remote.origin.url)
 if [ "$CURRENT_REPO" != "$DEFAULT_REPO" ]; then 
   echo "The Repository currently used is not the default Mailcow Repository."
   echo "Currently Repository: $CURRENT_REPO"