Make oz include githash when building interim RPM builds

Greetings,

GIT: [PATCH] Include githash when building pre-release packages

The attached patch follows the packaging process similar to aeolus-conductor by including a datestamp and githash in any pre-release RPM builds. A pre-release is any oz release where %{release} starts with '0'. Any pre-release rpm builds (make rpm) will include a datestamp and githash in the %{release} field. Any non pre-release builds will appear as normal.

Comments welcome.

Thanks, James