The SHA-1 tag of a server image is generated by the shared function
(sha1tree) in testserver_util.sh. The sha1tree function sorts the files
by the their SHA-1 and use the accumulated results as the TAG. So that,
we can assign the same SHA-1 value to a server on all the platforms.
Change-Id: If87ac72f7a9c5cdebef04977480d27b26a701b73
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@qt.io>
Build and cache docker images based on the configurations in testserver.
1. Move the shared Docker files to common/shared/testserver
2. Deploy boot2docker image into VirtualBox via docker-machine commands.
3. Build and tag the docker images by the SHA-1 of server context.
Change-Id: Ic5a588e5cc5e753ec4c4e2e1bc79917bbd03f95d
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
