Explicitly include versioninfo in tarball.

The most recent sync of openstack-common setup.py/version.py code
seems to have cause quantum/versioninfo to disappear from the tarball.
(see git commit d65bca8)

This updates MANIFEST.in to explicitly include that file and seems
to resolve the issue.

Fixes LP Bug #1077035.

Change-Id: I5fb395c15ea998da00b11e66947d1b1ea3665ea0

MANIFEST.in

@@ -1,5 +1,6 @@
 include AUTHORS
 include ChangeLog
+include quantum/versioninfo
 
 exclude .gitignore
 exclude .gitreview