PostGIS schema tests should try to trim out extraneous schema before comparison

[jng]

I am currently running the PostgreSQL provider test suite against postgis docker containers and we are currently getting various false positive test case failure because the postgis template database in these docker containers contain extra schemas like:

• tiger
• tiger_data
• topology

For convenience, such extra schemas should not derail the schema content comparison. We should try to weed out such schemas before dumping it out to file for comparison where possible.