This allows init-repository to be used with servers mirroring only a
portion of the qt5 submodules.  Any missing modules will be cloned from
the canonical upstream URLs.

Change-Id: I4b266edd2ec7d49126578b54eace6de6de629b56
Sanity-Review: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Jason McDonald <jason.mcdonald@nokia.com>