CursorAdapter: dont register ContentObserver in basic constructor

when using LoaderCallbacks we dont want to set
FLAG_REGISTER_CONTENT_OBSERVER in the adapter as that
will cause us to leak our context on configuration changes

also super sets context so no need to do it again

Change-Id: I08da5d2672df69da968bba28c206e57e1aecb389
Merge pull request #151 from drewis/dev

CursorAdapter: dont register ContentObserver in basic constructor