Fix invalid usage of cf app & cf delete
Issue:http://rnd-github.huawei.com/paas/cli/issues/9

Before Fix: If cf user does
'cf app cf-env blahablaha'
then its success

'cf delete cf-env blahablaha'
then its success

After Fix:If cf user does
'cf app cf-env blahablaha'
then it will fail with proper reason

'cf delete cf-env blahablaha'
then it will fail with proper reason