Improve UDPLite tests.

gtests/net/packetdrill/tests/bsd/udplite/udplite-cscov-sockopt.pkt

  0.000 socket(..., SOCK_DGRAM, IPPROTO_UDPLITE) = 3
+ 0.000 getsockopt(3, IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV, [0], [4]) = 0
 +0.000 setsockopt(3, IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV, [-1], 4) = -1 EINVAL (Invalid parameter)
 +0.000 setsockopt(3, IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV, [0], 4) = 0 
 +0.000 setsockopt(3, IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV, [1], 4) = -1 EINVAL (Invalid parameter)
@@ -13,6 +14,7 @@
 +0.000 setsockopt(3, IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV, [65536], 4) = -1 EINVAL (Invalid parameter)
 +0.000 setsockopt(3, IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV, [4294967295], 4) = -1 (Invalid parameter)
 // 
++0.000 getsockopt(3, IPPROTO_UDPLITE, UDPLITE_RECV_CSCOV, [0], [4]) = 0
 +0.000 setsockopt(3, IPPROTO_UDPLITE, UDPLITE_RECV_CSCOV, [-1], 4) = -1 EINVAL (Invalid parameter)
 +0.000 setsockopt(3, IPPROTO_UDPLITE, UDPLITE_RECV_CSCOV, [0], 4) = 0
 +0.000 setsockopt(3, IPPROTO_UDPLITE, UDPLITE_RECV_CSCOV, [1], 4) = -1 EINVAL (Invalid parameter)

gtests/net/packetdrill/tests/bsd/udplite/udplite-port-unreachable-alt.pkt

+// Connect the socket.
+ 0.000 socket(..., SOCK_DGRAM, IPPROTO_UDPLITE) = 3
++0.000 bind(3, ..., ...) = 0
++0.000 connect(3, ..., ...) = 0
+// Trigger the ICMP message.
++0.050 write(3, ..., 1000) = 1000 
++0.000 > udplite(1000, 0)
++0.000 < [udplite(1000, 0)] icmp unreachable port_unreachable
+// Check if applications get notified.
+//+0.050 getsockopt(3, SOL_SOCKET, SO_ERROR, [ECONNREFUSED], [4]) = 0
++0.050 getsockopt(3, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
+// Termination of the test.
++0.000 close(3) = 0