[ Merge of http://go/wvgerrit/110903 ]
This CL adds the ability to set the renewal server on the command
line, and adds some comments to the build scripts' README file to
explain how to test a server rollout.
Bug: 173031207
Test: WV unit/integration tests
Change-Id: Ibe71e77469c94601627fb85a1ad4654553d3eb1a
Change-Id: I7e9bfc873c78e26c0cece113dc8a3d08cd9163db