Fix the Watched Review Request resource with local sites, and add tests.

The GET handler for the Watched Review Request resource didn't accept
local IDs for review requests, causing it to be pretty useless there.
Now it takes the proper IDs.

Unit tests were added for this, and for all other missing cases.
Merge branch 'release-1.6.x' into release-1.7.x
Merge branch 'release-1.7.x'