Description of problem:
"Can't modify frozen hash" error is raised when trying to delete smart proxy via API or hammer, though proxy itself is deleted.
Works correctly via UI.

Example:
# Create using hammer
> # hammer -v -u admin -p changeme --output=csv proxy create --url="https://sat6.com:12370" --name="test"
> Message,Id,Name
> Smart proxy created,7,test

# Read info
> # hammer -v -u admin -p changeme proxy info --name="test"
> Id:            7
> Name:          test
> URL:           https://sat6.com:12370

# Try to delete via hammer
> # hammer -v -u admin -p changeme proxy delete --name="test"      
> [ERROR 2016-11-15 02:48:39 API] 500 Internal Server Error
> [ERROR 2016-11-15 02:48:39 Exception] Can't modify frozen hash
> Could not delete the proxy:
>  Can't modify frozen hash
> [ERROR 2016-11-15 02:48:39 Exception] 
> RestClient::InternalServerError (500 Internal Server Error):

# Read info one more time
> # hammer -v -u admin -p changeme proxy info --name="test"  
> [ERROR 2016-11-15 02:49:45 Exception] Error: smart_proxy not found
> Error: smart_proxy not found
> [ERROR 2016-11-15 02:49:45 Exception] 
> HammerCLIForeman::ResolverError (smart_proxy not found):

# Try to delete another proxy via API
> Making HTTP DELETE request to https://sat6.com/api/v2/smart_proxies/8 with options {'verify': False, 'auth': ('admin', 'changeme'), 'headers': {'content-type': 'application/json'}} and no data.
> Received HTTP 500 response: {
>  "error": {"message":"Can't modify frozen hash"}


Version-Release number of selected component (if applicable):
Satellite 6.3.0 Snap 6.0, Foreman 1.13.1-1

How reproducible:
Always

Steps to Reproduce:
1. ncat -kl -p 12370 -c "ncat sat6.com 9090"
2. hammer -v -u admin -p changeme --output=csv proxy create --url="https://sat6.com:12370" --name="test"
3. hammer -v -u admin -p changeme proxy info --name="test"
4. hammer -v -u admin -p changeme proxy delete --name="test"
5. hammer -v -u admin -p changeme proxy info --name="test"

Actual results:
Error and stacktrace are displayed.

Expected results:
Proxy should be deleted without errors.

Additional info: