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/dnsmasq.c

@@ -421,8 +421,8 @@ int main (int argc, char **argv)
     }
 
 #ifdef HAVE_INOTIFY
-  if ((daemon->port != 0 || daemon->dhcp || daemon->doing_dhcp6)
-      && (!option_bool(OPT_NO_RESOLV) || daemon->dynamic_dirs))
+  if ((daemon->port != 0 && !option_bool(OPT_NO_RESOLV)) ||
+      daemon->dynamic_dirs)
     inotify_dnsmasq_init();
   else
     daemon->inotifyfd = -1;