xenapi: rpmbuild fixes

Fixes bug 1157695

This fix removes the parted dependency from the rpm specification file,
and also gets rid of the assumption, that the build-rpm.sh is executed
at a specific directory.

Change-Id: I1dcf9096a783a88bc09af0f4f4d5541a7e505748
fix relative file issue

Change-Id: I8dc9eb983f848cb40fe03651d88fc5ab9bffebd1