Fix intermittent SRP Pub/Sub test failures

SRP unsubscribes asynchronously, so occasionally not all messages were delivered prior to unsubscribe. Test will now unsubscribe on connection close instead.
Use connection pools in all tests

The test suite creates a lot of connections. Use connection pooling where possible to minimize risk of Socket BindExceptions.
Clean up Connection integration tests

- Test multi for all applicable connection types

- Clean up unused code

- Remove redundant long-running pubsub test
Add missing client types to parameterized tests
Cleanup test application context