Merge branch 'stable-2.16' into stable-3.0

* stable-2.16:
  Update Gerrit API to 2.16.21
  Update Gerrit API to 2.15.19
  Update Gerrit API to 2.14.21

Change-Id: I2433e7717fd5123b3d64953c01c13ddcfb2cd9a8