mw/etcd: revert 'add fallthrough'

This removes 'fallthrough' for *etcd* which is not needed. This was
added in 00f5c7797 but is totally not needed and creates backwards
incompat behavior even.

Thanks to @johnbelamaric for pointing this out in #925.

middleware/etcd/setup.go

@@ -74,8 +74,6 @@ func etcdParse(c *caddy.Controller) (*Etcd, bool, error) {
 				switch c.Val() {
 				case "stubzones":
 					stubzones = true
-				case "fallthrough":
-					etc.Fallthrough = true
 				case "debug":
 					etc.Debugging = true
 				case "path":