Add zuul version to status.json
Add zuul version to status.json

It'll help us to determine whether we're running a version of zuul that has
added support for some new feature.

The version_string() from pbr's version_info used to collect zuul version.

Change-Id: Id451f15538258ab2dec8e3e8f000cff4a8b7b20d

gooddata/zuul,wikimedia/integration-zuul,devdattakulkarni/zuul_messaging,gooddata/zuul,gooddata/zuul,wikimedia/integration-zuul,wikimedia/integration-zuul,gooddata/zuul,wikimedia/integration-zuul,devdattakulkarni/zuul_messaging,gooddata/zuul,devdattakulkarni/zuul_messaging