Only bring down the interface at startup time if it is not already up and

running.  ndhc does its job entirely with raw sockets before a lease is
established, so it will work just fine, and this change allows for the dhcp
client to be re-run without causing downtime on an interface.

ndhc/netlink.c

@@ -40,14 +40,6 @@
 #include "arp.h"
 #include "log.h"
 
-enum {
-    IFS_NONE = 0,
-    IFS_UP,
-    IFS_DOWN,
-    IFS_SHUT,
-    IFS_REMOVED
-};
-
 static struct mnl_socket *mls;
 
 static void nl_close(struct client_state_t *cs)