Add docstring from LocalManifestMaker.add_defaults
Add docstring from LocalManifestMaker.add_defaults

A not-so-recent change to setuptools [1] has resulted in the inclusion
of a docstring from distutils that uses broken rST.

  docstring of pbr.packaging.LocalManifestMaker.add_defaults:11:Definition
  list ends without a blank line; unexpected unindent.

Resolve the issue by simply redefining the docstring.

[1] https://github.com/pypa/setuptools/compare/252ee6f...f1cf491f
[2] https://github.com/python/cpython/blob/3.4/Lib/distutils/command/sdist.py#L217-L229

Change-Id: I84b5097bc31af601061a77dfea9d6a6f38b018cc
Signed-off-by: Stephen Finucane <492121341a95b3c3aab646bed44634f739dd019b@redhat.com>

openstack-dev/pbr,openstack-dev/pbr,openstack-dev/pbr