I22 connection tests did not fail when they weren't mocking

[callumforrester]

#847 appears to have been caused by #841 not passing mock=True to the DeviceInitializationController, that should have caused a timeout failure when the CI tried to connect to PVs that don't exist on its network, instead the tests passed after a very long time, suggesting that something was timing out but not failing the test, perhaps an exception was being swallowed.

This issue is to investigate and prevent recurrence

Acceptance Criteria

• The cause of the non-failure is known
• A regression test/tests are in place to prevent recurrence

[callumforrester]

Tagging @DominicOram and @DiamondJoseph for awareness

[DiamondJoseph]

make_all_devices returns the connected devices and also collects all of the exceptions that were raised.
As discussed, the tests should have accounted for checking the collected exceptions.

[rtuck99]

This is fixed in #858