Pin glance dependency to pre-grizzly versions.

Fixes bug 1132835

* tools/pip-requires: Changes in recent glance prevent nose from
running tests in essex nova, resulting in a "Ran 0 tests" success
result. This change pins the dependency on glance to ensure grizzly
versions are not used in nova stable/essex.

Change-Id: Ia962287b5b23b5b536a4b7d3d10bb005c1c0eba9