Check policy present in quantum before deleting it.
Pass policy_name and project_name arguments to verify
if policy is present in quantum.

To avoid 'TypeError' check if 'output' is not None before
checking for a string in 'output'.

Change-Id: I24a8e65c7c0af130c54b9e457bbaf0e2fb76c19d
Merge "Check policy present in quantum before deleting it. Pass policy_name and project_name arguments to verify if policy is present in quantum." into R2.0