Description of problem:
The user should not be able to create a cluster with both gluster_serice and virt_service enabled. 

Version-Release number of selected component (if applicable):
add cluster --name aasdfsdfaslalala --cpu-id 'Intel SandyBridge Family' --gluster_service True --virt_service False --datacenter-name Default 

How reproducible:
100%

Steps to Reproduce:
1. run rhsc-shell
2. connect to the api
3. run the command "add cluster --name aasadsfdfsdfaslalala --cpu-id 'Intel SandyBridge Family' --gluster_service True --virt_service True --datacenter-name Default"

  
Actual results:
cluster was successfully created with both gluster_service and virt_service set to True.

Expected results:
Cluster should not be created. HTTP 40X should have been sent from the rhsc ovirt-engine with an error message.


Additional info:
also should not be able to create a cluster with both options off.