Fixesxamarin/maccore#658
When a MidiThruConnection is created but for some reason is not disposed
the system keeps it alive even between app/simulator restarts, if you want
to clean the connections you must reset contents and settings from simulator.
In order to avoid this test from failing randomly and since the intent of the
test is to check if `MidiThruConnection.Find` works we change the assert to
`>= 2` since this is at least the number of connections we expect.
Rolf Bjarne Kvinge
Alex Soto