util: netdevip: Include vircommand.h

Not including the header causes

  util/virnetdevip.c:520:5: error:
  unknown type name 'virCommandPtr'; did you mean 'virCondPtr'?
    virCommandPtr cmd = NULL;
    ^~~~~~~~~~~~~

and plenty more similar failures when compiling on FreeBSD.

src/util/virnetdevip.c

@@ -31,6 +31,7 @@
 #include "virlog.h"
 #include "virstring.h"
 #include "virutil.h"
+#include "vircommand.h"
 
 #if HAVE_GETIFADDRS
 # include <ifaddrs.h>