buildlet: unexport WaitUntilVMExists method

This change modifies the WaitUntilVMExists method and sets it to
not be exported. It will never be directly called by anything outside
of the EC2Client.

Updates golang/go#36841

Change-Id: If6dfea8c4c191036c8fadd9ad8767e85e55cd224
Reviewed-on: https://go-review.googlesource.com/c/build/+/247400
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alexander Rakoczy <alex@golang.org>

buildlet/ec2.go

@@ -71,7 +71,7 @@ func (c *EC2Client) StartNewVM(ctx context.Context, buildEnv *buildenv.Environme
 	if err != nil {
 		return nil, err
 	}
-	if err = c.WaitUntilVMExists(ctx, vm.ID, opts); err != nil {
+	if err = c.waitUntilVMExists(ctx, vm.ID, opts); err != nil {
 		return nil, err
 	}
 	// once the VM is up and running then all of the configuration data is available
@@ -100,8 +100,8 @@ func (c *EC2Client) createVM(ctx context.Context, config *cloud.EC2VMConfigurati
 	return inst, nil
 }
 
-// WaitUntilVMExists submits a request which waits until an instance exists before returning.
-func (c *EC2Client) WaitUntilVMExists(ctx context.Context, instID string, opts *VMOpts) error {
+// waitUntilVMExists submits a request which waits until an instance exists before returning.
+func (c *EC2Client) waitUntilVMExists(ctx context.Context, instID string, opts *VMOpts) error {
 	if err := c.client.WaitUntilInstanceRunning(ctx, instID); err != nil {
 		return fmt.Errorf("failed waiting for vm instance: %w", err)
 	}

buildlet/ec2_test.go

@@ -190,7 +190,7 @@ func TestWaitUntilInstanceExists(t *testing.T) {
 	if gotErr != nil {
 		t.Fatalf("createVM(ctx, %v, %v) failed with %s", vmConfig, opts, gotErr)
 	}
-	gotErr = c.WaitUntilVMExists(ctx, gotVM.ID, opts)
+	gotErr = c.waitUntilVMExists(ctx, gotVM.ID, opts)
 	if gotErr != nil {
 		t.Fatalf("WaitUntilVMExists(%v, %v, %v) failed with error %s", ctx, gotVM.ID, opts, gotErr)
 	}