fix requirements.txt in manila-ui and python-manilaclient
That packages has requirements. It makes the fpm build wrong
packages for ubuntu. Easiest way to avoid problem --- just ignore some
requirements when building the packages. It's simple and it works
because we know that on ubuntu that dependencies already satisfied.
Add manila projects as submodules and switch its to stable/mitaka.
Fix requirements to be compatible with ubuntu 14.04.
Change pre_build_hook to building deb packages from python source