Fix Makefile for XenServer builds

The provided Makefile failed to build the agent rpm for XenServer, using
the 6.1 ddk:
- version info was using only python instead of python2.6
- Failed to retrieve version info - bad paths
- Non unattended yum instruction - added -qy
- unpackaged files (pyc, pyo) halted the build. - added defines

Change-Id: I405aafe5df8a5955cb9f23bcca34037d557bae63