adb: fix `adb reverse` when adbd has multiple transports.

Plumb the transport that we received the adb reverse request on through
to reverse_service, instead of trying to get a unique transport on
devices that have multiple active transports (e.g. a device with USB
(even unplugged) connected via TCP).

Bug: http://b/37066218
Bug: http://b/71898863
Test: `echo foo | nc -l 12345 & adb reverse tcp:12345 tcp:12345; adb shell nc localhost 12345` on a device connected via TCP
Change-Id: Iae199ae787f2e344126bbcacca8544cfc9844a4c
(cherry picked from commit 44899eeb)