Finding sagas based on an association value now returns a sorted set

This prevents deadlocks by lock being acquired in different orders.
Fixed typo
Made test case more resilient against test ordering

This test suite uses a Spring context, but some tests modify the state of beans. They have been annotated with @DirtiesContext
Fixed issue where events for Saga-in-creation where not handled

When an event was received while a saga was being created, these events would
not be handled by that saga instance. This could happen when a Saga schedules
an event in the @StartSaga handler, and the schedule triggers before the
handler completed.

Issue #AXON-188 Fixed
Fixed issue with SagaMethodHandlerInspector returning null values