SQLite uses synchronous mode by default, which will synchronously write
data to disk. This will increase durability of data at the expense of
performance. The test suite does not need data to be durably written
to disk, so disabling synchronous mode results in a speeding up the
full test suite by about 20 seconds.
Change-Id: I5ca1ab1e8691e912d801fe1002dff752c82f3d5d
dd5def9237