Make sure that Ping success removes mailbox from error list

* We keep track of sync errors and have an increasing backoff for
* Make sure that a successful Ping (i.e. one that received a response
  at the specified timeout) clears the sync error state for the
  pinging mailbox

Change-Id: I35d188aa04618e7604bf6a7905e2ce6992ee3c54
2 files changed