Removes MANIFEST.in as it is not needed explicitely by PBR
Removes MANIFEST.in as it is not needed explicitely by PBR

This patch removes `MANIFEST.in` file as pbr generates a sensible
manifest from git files and some standard files and it removes
the need for an explicit `MANIFEST.in` file.

Change-Id: I9838d042ec3cffa047e95f2c1a8000d63cd55cab

openstack/python-barbicanclient