ansible: fix versioning specifier
Created by: rjw57
As noted in [1], the "compatible release" version semantics are a little unexpected in that "2.7" is considered compatible with "2.6". Using "2.6.0" and "2.7.0" should result in the expected behaviour.
[1] https://www.python.org/dev/peps/pep-0440/#compatible-release