selftests: tc-testing: fix tunnel_key failure if dst_port is unspecified

After commit 1c25324c ("net/sched: act_tunnel_key: Don't dump dst port
if it wasn't set"), act_tunnel_key doesn't dump anymore the destination
port, unless it was explicitly configured. This caused systematic failures
in the following TDC test case:

 7a88 - Add tunnel_key action with cookie parameter

Avoid matching zero values of TCA_TUNNEL_KEY_ENC_DST_PORT to let the test
pass again.
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/tc-testing/tc-tests/actions/tunnel_key.json

@@ -605,7 +605,7 @@
         "cmdUnderTest": "$TC actions add action tunnel_key set src_ip 10.10.10.1 dst_ip 10.10.10.2 id 7 index 4 cookie aa11bb22cc33dd44ee55ff66aa11b1b2",
         "expExitCode": "0",
         "verifyCmd": "$TC actions get action tunnel_key index 4",
-        "matchPattern": "action order [0-9]+: tunnel_key.*set.*src_ip 10.10.10.1.*dst_ip 10.10.10.2.*key_id 7.*dst_port 0.*csum pipe.*index 4 ref.*cookie aa11bb22cc33dd44ee55ff66aa11b1b2",
+        "matchPattern": "action order [0-9]+: tunnel_key.*set.*src_ip 10.10.10.1.*dst_ip 10.10.10.2.*key_id 7.*csum pipe.*index 4 ref.*cookie aa11bb22cc33dd44ee55ff66aa11b1b2",
         "matchCount": "1",
         "teardown": [
             "$TC actions flush action tunnel_key"