plugin/reload: disable for now (#1511)

Reloading should work (kill -TERM reload the coredns process), but a lot
of plugins can't handle it proper. Disable to reload plugin until we fix
(most) of the plugins

core/dnsserver/zdirectives.go

@@ -11,7 +11,6 @@ package dnsserver
 // care what plugin above them are doing.
 var Directives = []string{
 	"tls",
-	"reload",
 	"nsid",
 	"root",
 	"bind",