Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=2124520

Description of problem:
Changing the Smart Proxy field post the curl command is generated during registration failed with an error.

"There was an error while generating the command, see the logs for more information."

How reproducible:
100%

Steps to Reproduce:
1. Go to Foreman WebUI > Hosts -> Register Host
2. Select Smart Proxy parameter as Smart Proxy server FQDN, select other fields such as Host Group, Activation Key and then click on Generate
3. Once the Curl command is generated, change the Smart Proxy parameter again to default (Foreman) and regenerate the curl command by hitting Generate.

Actual results:
No Curl command generated again for host registration with Foreman and throwing the following message-

"There was an error while generating the command, see the logs for more information."

Expected results:
After changing the Smart Proxy parameter and hitting the Generate, another curl command should be created to register the host.