Use read_rows_flat to test broken sstables.
Use read_rows_flat to test broken sstables.

The previous code was using mp_row_consumer_k_l to be as close to the
tested code as possible.

Given that it is testing for an unhandled exception, there is probably
more value in moving it to a higher level, easier to use, API.

This patch changes it to use read_rows_flat().

Signed-off-by: Rafael Ávila de Espíndola <1975039f9046bf513b77c0c5639a0efc25f00e7f@scylladb.com>
Message-Id: <20181210235016.41133-1-1975039f9046bf513b77c0c5639a0efc25f00e7f@scylladb.com>

avikivity/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla