Remove runtime dependency on pbr
Remove runtime dependency on pbr

Pbr is a very heavy package to depend on. It requires git-core, which is
16 MiB on my Fedora. We only use it to detect the version, which can be
done without pbr by any consumer (e.g. with importlib_metadata).

This is technically a breaking change, although since ironic-lib is an
internal library it should not be an issue.

Change-Id: I6f5ee64226ffc6a30804c09bb28b3d6680b095d1

openstack/ironic-lib