selftests/vsock: avoid false-positives when checking dmesg

Sometimes VMs will have some intermittent dmesg warnings that are
unrelated to vsock. Change the dmesg parsing to filter on strings
containing 'vsock' to avoid false positive failures that are unrelated
to vsock. The downside is that it is possible for some vsock related
warnings to not contain the substring 'vsock', so those will be missed.

Fixes: a4a65c6fe08b ("selftests/vsock: add initial vmtest.sh for vsock")
Reviewed-by: Simon Horman <[e-mail]>
Signed-off-by: Bobby Eshleman <[e-mail]>
Reviewed-by: Stefano Garzarella <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/vsock/vmtest.sh

···
 	local rc
 
 	host_oops_cnt_before=$(dmesg | grep -c -i 'Oops')
-	host_warn_cnt_before=$(dmesg --level=warn | wc -l)
+	host_warn_cnt_before=$(dmesg --level=warn | grep -c -i 'vsock')
 	vm_oops_cnt_before=$(vm_ssh -- dmesg | grep -c -i 'Oops')
-	vm_warn_cnt_before=$(vm_ssh -- dmesg --level=warn | wc -l)
+	vm_warn_cnt_before=$(vm_ssh -- dmesg --level=warn | grep -c -i 'vsock')
 
 	name=$(echo "${1}" | awk '{ print $1 }')
 	eval test_"${name}"
···
 		rc=$KSFT_FAIL
 	fi
 
-	host_warn_cnt_after=$(dmesg --level=warn | wc -l)
+	host_warn_cnt_after=$(dmesg --level=warn | grep -c -i 'vsock')
 	if [[ ${host_warn_cnt_after} -gt ${host_warn_cnt_before} ]]; then
 		echo "FAIL: kernel warning detected on host" | log_host "${name}"
 		rc=$KSFT_FAIL
···
 		rc=$KSFT_FAIL
 	fi
 
-	vm_warn_cnt_after=$(vm_ssh -- dmesg --level=warn | wc -l)
+	vm_warn_cnt_after=$(vm_ssh -- dmesg --level=warn | grep -c -i 'vsock')
 	if [[ ${vm_warn_cnt_after} -gt ${vm_warn_cnt_before} ]]; then
 		echo "FAIL: kernel warning detected on vm" | log_host "${name}"
 		rc=$KSFT_FAIL