Correct a SQLite unit test

The unit test that is supposed to test read-only transactions is
missing the transaction.  This test was cloned from the CTS test; the
CTS test is correct. The read-only transaction was dropped for some
reason.

The failure rate of this test is pretty low.  If the read operations
completed before the write transaction was committed, then the test
passed.  Rarely, the test would fail in local testing.

The change was verified by injecting a 1s sleep in the reader routine,
after the routine advanced past the Phaser but before the routine read
from the database.  That change ensured that the write transaction
would be committed before the last read operation, and the reader
routine would throw.

Bug: 319435199

Test: atest
 * FrameworksCoreTests:android.database
Change-Id: I54d89508d3e6907ff53dd04dadb1d2c1815c276f