Enable client on netbsd and dragonfly

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

client/client_unix.go

@@ -1,4 +1,4 @@
-// +build linux freebsd openbsd darwin solaris illumos
+// +build linux freebsd openbsd netbsd darwin solaris illumos dragonfly
 
 package client // import "github.com/docker/docker/client"