Fix for multi-row INSERT capability test

Prior to commit 8070cbde716a247f8b31c1334c80fa53327e6d8e, sqlalchemy used
'supports_multirow_insert' instead of 'supports_multivalues_insert'. Let's
support both for now.

Change-Id: I3a40e52cc7610befd3c2c887a3b1af6acafc1208