Description of problem:

Adding new parameter in undercloud.conf file to set the overcloud domainname instead of modifying the undercloud configuration files like : 

/etc/nova/nova.conf 
/etc/neutron/dhcp_agent.ini


Version-Release number of selected component (if applicable):
RHEL OSP 8

How reproducible:
Everytime. 

Steps to Reproduce:
1.
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3.

Actual results:
Currently there is no parameter in undercloud.conf file to set the domainname of overcloud nodes. 

Expected results:
Having some sort of domain parameter in undercloud.conf can avoid editing the configuration files and restarting services on undercloud node

Additional info:

Clouddomain parameter used in yaml file, alone it's not sufficient to set the domainname on overcloud nodes. We need to edit the files manually on undercloud node and then restart the services to have the desired overcloud domainname.