Merge branch 'stable-2.14'

* stable-2.14:
  Let ExternalIdsUpdate take care to evict accounts from the account cache
  Don't index missing accounts
  AccountCache: Add getOrNull method that returns null for missing account
  AccountCache: Document get and getIfPresent methods

Change-Id: I263787704b9e11c19148ba855cb62ef17a1f0e99