bridge: Fix double free in cockpit_channel_ready()

For base64 channels we were freeing the decoded payload twice.

Closes #1515
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
bridge: Allocate enough space for base64 data

Follow the GLib documentation guidelines for allocating enough
space for base64 encoded/decoded data.

Closes #1516
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
tools: Fix make-rpms on recent Fedora 21

There's a lot of default output on Fedora 21 by default, and this
completely breaks make-rpms. Add --quiet to make-rpms to fix this.

Closes #1527
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>