Fix pasta_opts compose test to verify MTU option

Use podman exec to check ip link MTU instead of ncat-based host
connectivity test which does not actually validate pasta options.

Signed-off-by: Lokesh Mandvekar <lsm5@redhat.com>

test/compose/pasta_opts/docker-compose.yml

@@ -1,5 +1,5 @@
 services:
   alpine:
     image: alpine
-    network_mode: "pasta:--ipv4-only,-a,10.0.2.0,-n,24,-g,10.0.2.2,--dns-forward,10.0.2.3,--mtu,1280,--no-ndp,--no-dhcpv6,--no-dhcp"
-    command: sh -c "echo teststring | nc 10.0.2.2 5001"
+    network_mode: "pasta:--ipv4-only,--mtu,1280"
+    command: ["top"]

test/compose/pasta_opts/setup.sh

@@ -1,8 +0,0 @@
-# -*- bash -*-
-
-# create tempfile to store nc output
-OUTFILE=$(mktemp)
-# listen on a port, the container will try to connect to it
-ncat -l 5001 > $OUTFILE &
-
-nc_pid=$!

test/compose/pasta_opts/teardown.sh

@@ -1,4 +0,0 @@
-# -*- bash -*-
-
-kill $nc_pid &> /dev/null || true
-rm -f $OUTFILE

test/compose/pasta_opts/tests.sh

@@ -1,19 +1,6 @@
 # -*- bash -*-
 
-expected="teststring"
+ctr_name="pasta_opts-alpine-1"
 
-# Reading from the nc socket is flaky because docker-compose only starts
-# the containers. We cannot know at this point if the container did already
-# send the message. Give the container 5 seconds time to send the message
-# to prevent flakes.
-container_timeout=5
-while [ $container_timeout -gt 0 ]; do
-    output="$(< $OUTFILE)"
-    if [ -n "$output" ]; then
-        break
-    fi
-    sleep 1
-    container_timeout=$(($container_timeout - 1))
-done
-
-is "$output" "$expected" "$testname : nc received teststring"
+podman exec "$ctr_name" ip link
+like "$output" "mtu 1280" "$testname : mtu is set to 1280"