Parse slirp4netns net options with compat api

Parse the slirp4netns network options when called via compat api. The
options must be extracted from the NetworkMode string.

Fixes #10110

Signed-off-by: Paul Holzinger <paul.holzinger@web.de>

test/compose/slirp4netns_opts/docker-compose.yml

@@ -0,0 +1,5 @@
+services:
+  alpine:
+    image: alpine
+    network_mode: "slirp4netns:allow_host_loopback=true"
+    command: sh -c "echo teststring | nc 10.0.2.2 5001"

test/compose/slirp4netns_opts/setup.sh

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

test/compose/slirp4netns_opts/teardown.sh

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

test/compose/slirp4netns_opts/tests.sh

@@ -0,0 +1,6 @@
+# -*- bash -*-
+
+output="$(cat $OUTFILE)"
+expected="teststring"
+
+is "$output" "$expected" "$testname : nc received teststring"