Fix inference cancellation behavior

There is currently a possible race when canceling an inference, where
the inference may be the one currently running and a response will be
sent later or the inference response is already in the mailbox queue. To
handle these cases, the kernel will no longer process the inference
response for an inference that has been marked as aborted or is in the
process of being aborted.

Change-Id: Ifcd86591b09075f994ed2e903cb11ba7c0ee0418
Signed-off-by: Mikael Olsson <mikael.olsson@arm.com>