Switch Jenkins Jobs Back from Quantal to Precise

[Jeremy Stanley]

Given the shortened support duration provided by Ubuntu for non-LTS releases, it is not feasible to standardize on them as a test platform (latency involved in uptake by providers, as well as from validation and deployment by the Infra Team leaves very little of the support period remaining). As such, the current 16 Quantal slaves should be replaced with Precise slaves and Jenkins jobs transitioned to them, then the Quantal slaves can be deleted.

[Jeremy Stanley (fungi)]

New Precise slaves have been built, added into Jenkins and Nova unit tests run successfully from all of them via a manually-triggered test job.

The change to move jobs from quantal to precise node labels is https://review.openstack.org/28861 .

[Jeremy Stanley (fungi)]

The above change was implemented without incident, and the old quantal slaves have since been deleted from Jenkins and destroyed at the provider.