Enhancements to docimpact bug creation code

NB: This has not been tested yet, as launchpad staging server is down.

These changes:
* adds the gerrit review URL to the top of created bugs
(so bug assignees/triagers can look at the patch easily)

* set the tag of the bug to be the project/repo name, as is the
docs triaging standard

Change-Id: I1bc6a4081ac16ec2f8cf4cc419cec5b1fb03a6e2
Reviewed-on: https://review.openstack.org/34127
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins