Include yaml files
Upstream egg metadata MUST be preserved, it was a misguided guideline making packagers do it,
corrected in the meantime: https://fedorahosted.org/fpc/ticket/488
Issue is that egginfo cannot be fully regenerated by PBR when running from sdist,
like it is the case during rpmbuild.
Change-Id: I2263478cad435a90137906242d2c4391d1532220