pyfaf: only get fXX and fXX-updates tags from koji (no inherit)

Before this, we fetched fXX-update with inherit=True, which meant
that we would get f20 builds for f21 release, because f21-updates
inherits everything older. This could cause probable fixes to be
from an older release.
Merge pull request #343 from abrt/fix_fedora_get_released_builds

pyfaf: only get fXX and fXX-updates tags from koji (no inherit)