Fix RowsAffected tests for the case LastInsertId is not supported

Corrected failing tests. For the case where LastInsertId is not supported (postgresql), these tests must be skipped. 

Also there is another issue here. For Update method there should be SupportLastInsertId check, since its test was not failing, which causes an inconsistency.

One another issue is afais postgres returns affected row count. I am not sure if it is ok to depend on last insert id for retrieval of affected row count.