Add a hardcoded f18 destination, because that's how we roll

Adding f18 to the mocks to build with caused problems because now f18 packages
have no destination to be written to. This commit applies a bandaid to the
gangrenous arm that is the setup of the mock config. There will be a more
robust solution later today.
Merge pull request #106 from haus/gangrene

Add a hardcoded f18 destination, because that's how we roll