Force interactive mode for git-buildpackage run

Since the call to git-buildpackage is the "heart" of this service lets call
it always in interactive mode. Otherwise we don't see the important
information in OBS.

Signed-off-by: Jan Blunck <jblunck@infradead.org>
Version 1.3

Signed-off-by: Jan Blunck <jblunck@infradead.org>