Fix IllegalStateException in TvProvider

SQLiteOpenHelper will re-use the same DB instance for us.
We shouldn't close the DB gotten from SQLiteOpenHelper, which
may cause hazards to thread-safty.

Test: gts-tradefed run gts -m GtsTvTestCases
Bug: 38341610
Change-Id: Ia07e8a2aa11b8d86ce9c5cfa708cd60607bf7b34