Simplify ADB Wifi port listener

It seems the code was written at a time when the AdbDebuggingManager was
not guaranteed to be instantiated. This state necessitated duplicating
in ADBService the port listener from AdbDebuggingManager.

Since aosp/1326491, AdbDebuggingManager is always created which means we
can delete this workaround.

Test: Manual
Fixes: 402927103
Change-Id: I9e280319a0a8bfced40acb527927a34953f2c2ec