cloud/datastore: delete unused code in key.go, unit test.

Change-Id: Ice67a7ec494d64a43400f65b77aaa2cf75c96a9c
cloud/datastore: Fix one test case in un-indexable values

Change-Id: I087fe7f506f1b961ee15632007c2146cdea745ba
cloud: fix the broken build

- Fix the vanity URLs
- Add required index definition to run the integration test

Change-Id: I7a32d3110545789712b846938d430b50a4ef0ae4