Increase timeouts for Exchange sync; prevent early upload sync

* It's reported that 50% of third party users have issues syncing
  Calendar in Exchange
* In testing, it was determined that the server takes > 30 seconds
  to respond to a sync request initially, which is beyond our timeout
* Also, I found that the system SyncManager was trying to trigger an
  upload sync at the same time (i.e. before the sync session was
  established with the server)
* There are four changes here:
  1) Prevent upload syncs while the sync key is null or "0" ("0"
     is the initial state)
  2) Increase timeout for connection; at worst, this will
     cause a short extra delay in syncs with a bad connection, but this
     will be unnoticable to users
  3) Increase the read timeout for initial sync to twice that of
     regular syncs (the initial sync always seems to take longer)
  3) Reduce the lookback for calendar to two weeks (from one month);
     this is a better default anyway, and it probably reduces the server
     and client load a great deal
* Empirically, this solves the bug for a known completely repeatable

Bug: 2569162
Change-Id: I36b1c3e1e0b65f50d42e05f1830fed912191651f
2 files changed