Correcting getGlobalSchemaName to use the correct schema

Attempt to reproduce the problem reported in #741 but added a test that
covers the scenario based on current information. Perhaps the problem
can be reproduced in CI. There is also a chance that the test suite
harness makes this challenging to reproduce because of wrapping
transactions.

While these foreign key toggles appear to work in tests. When testing
the same migration operations within an application the contraint error
is reproducible and not fixed still.

Disable foreign key checks when removing temp tables