Description of problem:

When RHEV-H is managed by one RHEV-M then it is still possible to add the same RHEV-H to the other RHEV-M without any question or warning.
RHEV is enterprise solution and in enterprise environment there are quite often tens or hundreds hypervisors and at least 2 RHEV-M (prod and test purpose). So it is very easy to make a mistake and accidentally add wrong RHEV-H to the other Manager

Version-Release number of selected component (if applicable):
rhevm-3.5.8-0.1.el6ev.noarch

How reproducible:
every time

Steps to Reproduce:
1. set one RHEV-M1, add RHEV-H
2. set the other RHEV-M2
3. add RHEV-H already managed by RHEV-M1 to the other Manager (RHEV-M2)

Actual results:
No message that RHEV-H is already managed. It is possible to add RHEV-H every time

Expected results:
Warning message and ask for conformation

Additional info: