Require httplib2>=0.7.5

This patch bumps the httplib2 version to be greaten then 0.7.5 which
adds a RETRIES attribute which needs to be set in order to prevent
retrying requires on timeout which is a behavior that we do not want
as it can create orphaned objects that we can't detect.

See https://code.google.com/p/httplib2/issues/detail?id=124 for more
details.

Change-Id: Ib80255bef56d2c9b827b02e13f16d26b0e17d48a
Merge "Require httplib2>=0.7.5"