RDMA/addr: Fix some cancellation problems in process_req()

Fix following problems in process_req() relating to cancellation:

- Function is wrongly doing another addr_remote() when cancelled,
  which is not required.
- Make failure reporting immediate by using time_after_eq().
- On cancellation, -ETIMEDOUT was returned to the callback routine
  instead of the more appropriate -ECANCELLED (users getting notified
  may want to print/return this status, eg ucma_event_handler).

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>