tests: refactor file monitor test to make it more understandable

tests: refactor file monitor test to make it more understandable

The current file monitor unit tests are too clever for their own good
making it hard to understand the desired output.

Instead of trying to infer the expected events, explicitly list the
events we expect in the operation sequence.

Instead of dynamically building a matrix of tests, just have one giant
operation sequence that validates all scenarios in a single test.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>