Check if the repository-name exists

If the name exists exit with 0
The commented out section is ignored since it could be an other location after an update of the package.

This should close https://github.com/PirateBox-Dev/openwrt-temp-repository/issues/1
Merge pull request #2 from FriedZombie/patch-1

Check if the repository-name exists and exit
Fixes #1