Use the full release string when showing version

My Zuul version shows up as:

 $ zuul --version
 2.0.0.55

Since I have a local hack to slightly adjust the requirements, it is
really version 2.0.0.54 with my hack.  To help disambiguate this change
make the version string to report the full release string, ie including
the git commit.  Yields:

 $ zuul --version
 2.0.0.55.g1395090
 $

Where 1395090 is the commit sha1 of my cherry pick.  Ideally it would be
something like:  2.0.0.54.1.g1395090 to show up that one change is
diverging from upstream.

Change-Id: I32f5e8a1a84943e920f91ac1fa90784a4ac1fe6b
Merge "Use the full release string when showing version"