Add hostChanged service call; use it from UI (fixes #2148572)

* After a HostAuth has been changed for an EAS account, the SyncManager needs
  to be alerted so that it can take appropriate action
* Added hostChanged service call
* Send service call from AccountSetupExchange after a HostAuth is edited
* Stop running syncs and clear error states in hostChanged

Change-Id: I2311e2d00be81ea7829f5f4e38b2377f18c63f30
2 files changed