Make it easy to use the e2e tests to test upgrading a running master
by adding support for testing official release versions and writing a
simple script to first bring up and test the old version before
upgrading it and testing it again. Related to supporting in-place
upgrades of masters (#2524).
Merge pull request #2829 from a-robinson/upgrade

Make it easy to use the e2e tests to test upgrading a running master