Description of problem:
You are able to add rate with any arguments via REST API what could cause the unexpected error in UI.

Version-Release number of selected component (if applicable):
5.5.0.11

How reproducible:
100%

Steps to Reproduce:
1. Add rate via REST API with arguments
   {
    'description': 'test_rate',
    'rate': 1,
    'chargeback_rate_id':2 
   }
   chargeback_rate_id corresponds to the id of Storage Default chargeback rates 
2. Go to Cloud Intelligence -> Chargebacks -> Rates -> Storage
3. Click on Default chargeback rates

Actual results:
The rate is added successfully and after step 3 you will get page with "Unexpected error encountered"

Expected results:
Error message about incorrect arguments should be returned when you try to add rate, the result of step 3 shouldn't be page with error message 

Additional info:
Also you are able to add the rate with chargeback_rate_id argument which doesn't exist or not specify it at all.

The issue could be reproduced by using the cfme_tests tools. The code is below.

from utils.api import API
api = API ('https://ip_address/api/', auth=('login','password'))
data = {
        'description': 'test_rate_',
        'rate': 1, 
        'chargeback_rate_id':12 }

api.collections.rates.action.create(data)