Create a "myip" file inside the jail for use by the gated config file

generation code

tmcd/freebsd/jail/mkjail.pl

@@ -417,6 +417,13 @@ sub mkrootfs($)
 	}
     }
 
+    #
+    # Stash the control net IP if not the same as the host IP
+    #
+    if ($IP ne $hostip) {
+	mysystem("echo $IP >> $path/root/var/emulab/boot/myip");
+    }
+
     #
     # Get a list of all the plain files and create zero length versions
     # in the new var.