LU-15718 lnet: improve lnet_selftest speed

LU-15718 lnet: improve lnet_selftest speed

lets replace a global spinlock with atomic variables,
to avoid cpu power limit in testing.

Test-Parameters: trivial testlist=lnet-selftest
HPE-bug-id: LUS-10812
Signed-off-by: Alexey Lyashkov <alexey.lyashkov@hpe.com>
Change-Id: Ib12a3b3fe2fe300354e5a7c502bc6f5165e7d05c
Reviewed-on: https://review.whamcloud.com/47002
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>