No specific error message if Policy exists with same id

[SebastianOpriel]

Click on Policies>Create policy>Enter policy ID>Select Type as Time-Period-Restricted>Select date range and click on Create

Again follow the same to create a duplicate policy id:

Click on Policies>Create policy>Enter policy ID>Select Type as Time-Period-Restricted>Select date range and click on Create

Actual Result: It gives error message as "Failed creating policy". The user is not able understand root cause of the error.

Expected/Recommendation: Error message should be as "ID already exists" or some descriptive message.

Similar to: #745