osstest: hook FreeBSD flight into cr-daily-branch

osstest: hook FreeBSD flight into cr-daily-branch

Add the missing pieces so that cr-daily-branch knows how to create a
FreeBSD flight. This has been tested by calling `./cr-daily-branch
freebsd-master`.

Note that there are two missing pieces. The first one is correctly
setting the FREEBSD_<arch>_BUILDJOB environment variable when calling
make-freebsd-flight, without it the installer media will always be
picked from the configuration file. This requires keeping track of
previous FreeBSD successful build jobs, marking them as permanent and
fetching them from the database in order to pass them on the env
variable.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
---
v8.1:  fix ap-fetch-version-old for the freebsd-* branch
       (The remote branch has been changed to tested/master or
       tested/stable/<version> instead of plain master or stable/11.)

Changes since v6:
 - Set the path to the FreeBSD git trees in this patch.
 - Push to tested/master or tested/stable/<version> instead of using
   the same branches as the origin tree.

Changes since v5:
 - Add support for testing multiple FreeBSD branches, default to
   branch master.

Changes since v3:
 - Fix the daily-cron-email-* settings for FreeBSD branch flights.