Prevent from SQLiteException of locked databases

This CL ensures that opened cursors are always closed using
try-with-resources, and also prevents concurrent access to
opened cursors before they are closed using synchronized mehtods.

Bug: 299033978
Test: atest BluetoothInstrumentationTests
Change-Id: I48c04c46745e165142ae9569333b8ec647d3a0c3