mw/etcd: use context.TODO() in tests (#1000)

Go vet warning: fix use of context.

Fixes #997

Also make *auto*'s reload test less flaky by retrying
and then giving up.

middleware/etcd/lookup_test.go

@@ -20,7 +20,7 @@ import (
 )
 
 func init() {
-	ctxt, _ = context.WithTimeout(context.Background(), etcdTimeout)
+	ctxt = context.TODO()
 }
 
 // Note the key is encoded as DNS name, while in "reality" it is a etcd path.