rdbms: ignore DBO_NOBUFFER flag in IDatabase

rdbms: ignore DBO_NOBUFFER flag in IDatabase

Callers should use query batching instead. Without buffering, either
the RAM burden is shifted onto the RDBMS server (with MVCC vacuuming
also being stalled) or the RDBMS server has to keep adding locks as
the cursor advances. Also, if a caller does not read all the results
(possibly due to an exception), then the SQL commands sent/read get
out of sync, which is too fragile.

There are no DBO_NOBUFFER callers in WMF gerrit repos.

Change-Id: I3712149633d0f01bb6990e324e53dd58abba9cfd