Correct join for FKs with schema in SQL Server

Correct join for FKs with schema in SQL Server

Fixed 1.2 regression caused by :ticket:`4060` where the query used to
reflect SQL Server cross-schema foreign keys was limiting the criteria
incorrectly.

Additionally, added some rework of the inter-schema reflection tests
so that MySQL, MSSQL can be included, breaking out some of the
Postgresql-specific behaviors into separate requirements.

Fixes: #4234
Change-Id: I20c8e70707075f1767b79127c2c27d4b313c6515
(cherry picked from commit 9d5e117f6fcc38d8773bc943c615888dc8a3a819)