LU-10123 lnet: ensure peer put back on dc request queue

Upon async PUT request received from peer already in discovery
process, lnet_peer_push_event() was not handling the case where
peer could be on working/ln_dc_working queue. This could lead
for peer not to be re-dsicovered as expected, but left on
working queue and to be finally timed-out.

Also ensure that peer will not be put back on request queue by
event handler if discovery is already completed.

Signed-off-by: Bruno Faccini <bruno.faccini@intel.com>
Change-Id: Ic74a313c00edc1b8fdd14794d2c88411d12e0979
Reviewed-on: https://review.whamcloud.com/30147


Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Amir Shehata <amir.shehata@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Olaf Weber <olaf.weber@hpe.com>
Reviewed-by: Doug Oucharek <dougso@me.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>