We actually just build 3.6.4 and 3.7.1 images using 3.6.3 and 3.7.0
versions of plugins. We also deployed the resulting 3.6.4 image to prod.
Luckily for us 3.6.3 plugin tags match 3.6.4 and 3.7.0 tags match 3.7.1.
There was one exception which we were alredy checking out master for in
order to fix build errors. Now that there is a new reviewnotes tag for
3.6.4 we can drop the master checkout for that plugin and use the tag.
TL;DR this should be a noop for our images but is nice bookkeeping to
avoid surprises.
Change-Id: Ica8b3605ecb0f3f93747b904c39913800d1eee4e
ca630db7b2