Fix builddocker DNS resolution; add script to restart clean containers for all builddockers

Change-Id: Ibd239caa514c131d4ea03dab32f80d7209c17fea
Reviewed-on: http://review.couchbase.org/40806
Reviewed-by: Chris Hillery <ceej@couchbase.com>
Tested-by: Chris Hillery <ceej@couchbase.com>