InputCommon: Fix deadlock in EmulatedController::UpdateReferences().

[AdmiralCurtiss]

There's a deadlock here that can happen if thread A calls UpdateReferences() while thread B holds the DeviceContainer::m_devices_mutex and before releasing it also calls UpdateReferences(). The UpdateReferences() first locks the s_get_state_mutex, then locks the m_devices_mutex (indirectly first via the HasConnectedDevice() call, but also potentially later down the UpdateReferences() chain in eg. ControlExpression::UpdateReferences()). If m_devices_mutex is already locked by another thread that subsequently tries to acquire the s_get_state_mutex -- for example, the HotkeyScheduler thread calling UpdateInput() which in turn triggers a InvokeDevicesChangedCallbacks() which in turn also triggers UpdateReferences() -- they both try to lock the mutex the other thread already holds, deadlocking in the process.

This is the deadlock I mentioned in #11038.

[shuffle2]

Nice, i just got around to hooking up debugger and getting stacks and you fixed it already :)