qtqa: Run submodule update for module under test

When fetching all required sources to test one submodule,
init-repository script is used for all submodules except
for the one being tested. To get its possible submodules
as well, we have to run submodule update for it separately.

Change-Id: I6f6b79d82faa68fdc8307ae07c8ae1166cf0404c
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
Reviewed-by: Zeno Albisser <zeno.albisser@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>