Don't crash Launcher when attempting to endTransaction on an
already-closed DB.

Since the DB is already closed, if we can't end the
transaction, it should not put the code in a bad state.

Bug: 173162852
Test: manually tested backup and restore flow and existing tests
Change-Id: I2692d98f0a8efc8aeb6bfd826fe738e4436c6ee4
1 file changed