Don't create a useless inotify file desrcriptor when --port=0

If there are no dynamic configuration directories configured with
dhcp-hostsdir, dhcp-optsdir and hostsdir then we need to use inotify
only to track changes to resolv-files, but we don't need to do
that when DNS is disabled (port=0) or no resolv-files are configured.

It turns out that inotify slots can be a scarce resource, so not
using one when it's not needed is a Goood Thing.

Patch by HL, description above from SRK.

src/inotify.c

@@ -94,7 +94,7 @@ void inotify_dnsmasq_init()
   if (daemon->inotifyfd == -1)
     die(_("failed to create inotify: %s"), NULL, EC_MISC);
 
-  if (option_bool(OPT_NO_RESOLV))
+  if (daemon->port == 0 || option_bool(OPT_NO_RESOLV))
     return;
   
   for (res = daemon->resolv_files; res; res = res->next)