Extend presubmit to covert test and request (#1846)

Fix the casing *and* fix use of context as we were still referencing
the non-std lib context - no wondering how this could have worked...

test/grpc_test.go

@@ -1,13 +1,13 @@
 package test
 
 import (
+	"context"
 	"io/ioutil"
 	"log"
 	"testing"
 	"time"
 
 	"github.com/miekg/dns"
-	"golang.org/x/net/context"
 	"google.golang.org/grpc"
 
 	"github.com/coredns/coredns/pb"