Use real deviceId when validating Exchange account

* Since we're already checking for an existing account, we can
  send the actual deviceId, rather than "validate"
* The former code could cause user confusion and MSFT has
  suggested that we always use the actual id
* Also, avoid creating an extra service object

Bug: 5215726
Change-Id: I3b8406741cfb664483009d34624a3270ccabfa78
1 file changed