Further filter the query for detecting PIM originated changes.
Work around nasty consequences of Outlook's handling of incoming changes.

Outlook explicitly prevents a getChanges() call when it is sending
changes to the server. This leads to several nasty bugs/consequences -
all a result of the sync_ts not being updated due to no polling of
changes.

First round of attempts to fix this in a BC way.
A bit too greedy in keeping previous map entries.