Adding support for detecting RHEV Hypervisor in ansible_virtualization_type

Adding support for detecting RHEV Hypervisor and thus marking a machine as a guest inside RHEV.

Before:

(ansible-1.4.3)ansible ~/ansible > ansible rhev_guestvm -m setup  | grep virtualization
(ansible-1.4.3)ansible ~/ansible > 

After:

(ansible-1.4.3_dieter)ansible ~/ansible > ansible rhev_guestvm -m setup  | grep virtualization
        "ansible_virtualization_role": "guest", 
        "ansible_virtualization_type": "RHEV"
(ansible-1.4.3_dieter)ansible ~/ansible >