nit: Fix invokeStaleDummyVMTestWithStoragePolicy()

There were nits in invokeStaleDummyVMTestWithStoragePolicy() like
- The error message didn't contain necessary space
- IsVMPresent() can return an error, but lack of the error handling
- IsVMPresent() returns true/false, but didn't use ExpectEqual() and
  less code readability

This fixes those things.

Author: Kenichi Omichi

test/e2e/storage/vsphere/vsphere_volume_vsan_policy.go

@@ -335,8 +335,9 @@ func invokeStaleDummyVMTestWithStoragePolicy(client clientset.Interface, masterN
 	fnvHash := fnv.New32a()
 	fnvHash.Write([]byte(vmName))
 	dummyVMFullName := dummyVMPrefixName + "-" + fmt.Sprint(fnvHash.Sum32())
-	errorMsg := "Dummy VM - " + vmName + "is still present. Failing the test.."
+	errorMsg := "Dummy VM - " + vmName + " is still present. Failing the test.."
 	nodeInfo := TestContext.NodeMapper.GetNodeInfo(masterNode)
-	isVMPresentFlag, _ := nodeInfo.VSphere.IsVMPresent(dummyVMFullName, nodeInfo.DataCenterRef)
-	framework.ExpectNotEqual(isVMPresentFlag, true, errorMsg)
+	isVMPresentFlag, err := nodeInfo.VSphere.IsVMPresent(dummyVMFullName, nodeInfo.DataCenterRef)
+	framework.ExpectNoError(err)
+	framework.ExpectEqual(isVMPresentFlag, false, errorMsg)
 }