Increase the timeout for shutting down the exporter

One millisecond is quite short, and I was getting failures locally:

go test ./... + race in ./exporters/otlp
2020/12/14 18:27:54 rpc error: code = Canceled desc = context canceled
2020/12/14 18:27:54 context deadline exceeded
--- FAIL: TestNewExporter_withMultipleAttributeTypes (0.37s)
    otlp_integration_test.go:541: resource span count: got 0, want 1
FAIL
FAIL	go.opentelemetry.io/otel/exporters/otlp	5.278s

or

go test ./... + coverage in ./exporters/otlp
2020/12/14 17:41:16 rpc error: code = Canceled desc = context canceled
2020/12/14 17:41:16 exporter disconnected
--- FAIL: TestNewExporter_endToEnd (1.53s)
    --- FAIL: TestNewExporter_endToEnd/WithCompressor (0.41s)
        otlp_integration_test.go:246: span counts: got 3, want 4
2020/12/14 17:41:18 context canceled
FAIL
coverage: 35.3% of statements in ./...
FAIL	go.opentelemetry.io/otel/exporters/otlp	4.753s

exporters/otlp/otlp_integration_test.go

@@ -221,7 +221,7 @@ func newExporterEndToEndTest(t *testing.T, additionalOpts []otlp.GRPCConnectionO
 	<-time.After(40 * time.Millisecond)
 
 	// Now shutdown the exporter
-	ctx, cancel := context.WithTimeout(ctx, time.Millisecond)
+	ctx, cancel := context.WithTimeout(ctx, time.Second)
 	defer cancel()
 	if err := exp.Shutdown(ctx); err != nil {
 		t.Fatalf("failed to stop the exporter: %v", err)
@@ -525,7 +525,7 @@ func TestNewExporter_withMultipleAttributeTypes(t *testing.T) {
 	<-time.After(40 * time.Millisecond)
 
 	// Now shutdown the exporter
-	ctx, cancel := context.WithTimeout(ctx, time.Millisecond)
+	ctx, cancel := context.WithTimeout(ctx, time.Second)
 	defer cancel()
 	if err := exp.Shutdown(ctx); err != nil {
 		t.Fatalf("failed to stop the exporter: %v", err)