Allow 1:M tracking of Submodule Branches

Allow 1:M tracking of Submodule Branches

Use of the 'matching' config under 'allowSuperproject' only allows for a
1:1 mapping of branches[1]. This means only master of opnfvdocs can track
master of another project, and stable/stream can only track
stable/stream.

Dovetail needs the ability to track stable/danube from opnfvdocs master
branch, thus switching 'matching' to 'all' should allow this to work.

There does not appear to be any reason why we this current restriction
is needed and expect this was due to poor documentation on Gerrit's
part.

[1] https://gerrit.opnfv.org/gerrit/Documentation/user-submodules.html#acl_refspec

Change-Id: I9d7149801e2fe5b59c52ff3d11570f0dc40b4866
Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>