samba: Use upstream samba repo

Signed-off-by: Sam Lang <sam.lang@inktank.com>
samba: Only build master branch

Adds a branches-local-samba file for samba that
will only build the master branch of the samba repo.
The branches-local-samba script only outputs branches
listed in the PRIORITIZED list, skipping other branches
and tags.

Signed-off-by: Sam Lang <sam.lang@inktank.com>