Fix WTF crash related to ConversationCursor

* We weren't setting mPosition properly when moveToNext() failed in
  the underlying cursor
* Remove stack trace logging for expected situations
* Optimize long backward cursor moves
* Add some temporary logging for newly added code

Bug: 7012403
Change-Id: I8dcb97539f00dec84bdae74858d7b8efc5e55733
1 file changed