USB MIDI: Don't call openLocked on device unplug

When a USB MIDI device with multiple ports is
unplugged, onDeviceStatusChanged gets called
multiple times. The first time ends up opening a
port since there are still other open ports.

The fix here is to ignore onDeviceStatusChanged()
if close() was called before.

Also changed a continue to a break since that
condition almost never gets hit.

Bug: 232142589
Bug: 231496864
Test: Midi Keyboard that opens both input and output
for both peripheral and host mode

Change-Id: I973d55371cd16803ede192081531ca5f59847a51