MINOR: listener: add so_name sample fetch

Add a sample fetch for the name of a bind. This can be useful to
take decisions when PROXY protocol is used and we can't rely on dst,
such as the sample config below.

  defaults
    mode http
  listen bar
    bind 127.0.0.1:1111
    server s1 127.0.1.1:1234 send-proxy

  listen foo
    bind 127.0.1.1:1234 name foo accept-proxy
    http-request return status 200 hdr dst %[dst] if { dst 127.0.1.1 }
diff --git a/reg-tests/sample_fetches/so_name.vtc b/reg-tests/sample_fetches/so_name.vtc
new file mode 100644
index 0000000..c6211fa
--- /dev/null
+++ b/reg-tests/sample_fetches/so_name.vtc
@@ -0,0 +1,22 @@
+varnishtest "so_name sample fetche Test"
+
+#REQUIRE_VERSION=2.2
+
+feature ignore_unknown_macro
+
+haproxy h1 -conf {
+    defaults
+        mode http
+
+    frontend fe
+        bind "fd@${fe}" name foo
+        http-request return status 200 hdr so-name %[so_name]
+
+} -start
+
+client c1 -connect ${h1_fe_sock} {
+    txreq -url "/"
+    rxresp
+    expect resp.status == 200
+    expect resp.http.so-name == "foo"
+} -run