Change HAproxy for Glance API service

When uploading a big image (usually a RAW), the upload fails to happen
because of HAproxy timeout.
We need to change the HAproxy configuration to use another mode and also
increase the timeout to 2 hours (should be enough for regular images).

Closes-bug #503
Merge pull request #504 from enovance/glance-api-timeout

Change HAproxy for Glance API service