Updating a local git repo clone currently results in multiple calls
to self._contains_ref(), some of which appear to be redundant and can
be eliminated by minor tweaks to the logic in download().
Also drop redundant calls to os.path.exists(ud.clonedir) before
self.need_update(), since need_update() includes its own built-in
check for the existance of ud.clonedir.
(Bitbake rev: 61b0df5523afc8f805043f3adc9c106690e6f133)
Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>