don't enable "fast insert executemany" for ON CONFLICT etc

don't enable "fast insert executemany" for ON CONFLICT etc

Fixed issue where using the PostgreSQL "INSERT..ON CONFLICT" structure
would fail to work with the psycopg2 driver if it were used in an
"executemany" context along with bound parameters in the "SET" clause, due
to the implicit use of the psycopg2 fast execution helpers which are not
appropriate for this style of INSERT statement. Additional checks to
exclude this kind of statement from that particular extension have been
added.

Fixes: #6581
Change-Id: I3d6169e7e188dc087d1d1bfba9a42162db183265