IntResultReceiver: fix clearing on dispatch

Fixes an issue where mConsumer was cleared too early for any executor
other than Runnable::run, leading to an NPE when the Runnable is invoked
on the Executor.

Fixes: 265457058
Test: atest InputConnectionEndToEndTest
Change-Id: Ifc8e435e02520eb29c9631427daa5a1a1ea0ccf0