LU-15076 socklnd: lock ksnc_tx_queue list processing

LU-15076 socklnd: lock ksnc_tx_queue list processing

A GFP occurred in the ksocknal_find_timed_out_conn() while processing
ksnc_tx_queue list.

Add locking to this list.

Change-Id: I1f76683e5798c5015f11e3fa285db9613b1af906
Signed-off-by: Artem Blagodarenko <artem.blagodarenko@hpe.com>
HPE-bug-id: LUS-10248
Fixes: 25c1cb2c4d ("LU-9120 lnet: handle socklnd tx failure")
Reviewed-by: Chris Horn <hornc@cray.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-on: https://review.whamcloud.com/45179
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>