beakerrepos.py: pass --name explicitly
The current nightly composes identify themselves as just
"Fedora Rawhide" in the .treeinfo file, rather than distinguished by
date as in "Fedora-Rawhide-20170829.n.0". This means when they are
imported into Beaker they will all be considered as the same tree, even
though they are different snapshots.
As a workaround, pass --name when invoking beaker-import to make the
trees show up with their proper name.
This means we can't use 'location' as a fallback for 'compose_id'
anymore because the 'location' URL isn't usable as a distro tree name in
Beaker. But that should be okay since all recent compose messages have
a proper value for the 'compose_id' key.