Description of problem:
The Content source field gets blank after editing a provisioned host.
Editing back the provisioned host doesn't show the content source field.

Version-Release number of selected component (if applicable):
Satellite 6.3.3

How reproducible:
Yes it is reproducible

Steps to Reproduce:
1. Selecting the Content Source while provisioning, In this case host group does not have content source configured. Business requirement, hence selecting the content source manually while provisioning a host.
2. Once the host is provisioned, Editing the host should suppose to show the content source field which is appearing blank.
3. The content source field goes blank after editing the host. 

Actual results:
The content source field goes blank after editing the host. 


Expected results:
Editing the host should suppose to show the content source field 


Additional info:
In this case Host group does not have content source configured. User select host group and then select the content source according to business requirement.
This was working in Satellite 6.2