vclib: enable VM disk attach test

Follow up to PR #58534 , where this test was disabled due to a limitation in
govmomi/simulator.  The test passes as expected with godeps update of govmomi.

pkg/cloudprovider/providers/vsphere/vclib/virtualmachine_test.go

@@ -90,7 +90,7 @@ func TestVirtualMachine(t *testing.T) {
 
 		options := &VolumeOptions{SCSIControllerType: PVSCSIControllerType}
 
-		for _, expect := range []bool{true} { // TODO: vcsim needs to honor FileOperation to attach an existing disk
+		for _, expect := range []bool{true, false} {
 			attached, err := vm.IsDiskAttached(ctx, diskPath)
 			if err != nil {
 				t.Error(err)