Description of problem:
During an upgrade of RHEV-3.6.10 (upgraded since RHEV-3.3) and additionally migrating from out-of-band cluster for the manager to self-hosted, we ran into the issue that the manager was not able to add the hosted-engine host.


Version-Release number of selected component (if applicable):
* Running RHEV-3.6.10 with "rhevm" as management bridge
* Upgrading to RHV-4.0 by installing ovirt-hosted-engine-setup and bringing up a new engine, applying the backup from RHEV-3.6.10

How reproducible:
Always

Steps to Reproduce:
1. Install RHEV-manager with "rhevm" as management bridge (has been default until 3.5/3.6??)
2. Create backup of database
3. Install RHV-4 host with hosted-engine (a separated BZ will be filed because ovirt-hosted-engine-setup pulls in RHV-4.1 appliance during setup)
4. Restore backup from RHEV-3.6.10 on RHV-4.0 engine for upgrade
5. run "engine-setup"
6. shutdown engine as directed when engine-setup finished.
7. find ovirt-hosted-engine-setup starting the engine with "ovirtmgmt" as management interface whereas the hosts use "rhevm". 

Actual results:
ovirt-hosted-engine-setup creates unconditionally "ovirtmgmt" as bridge for the management interface.

Expected results:
ovirt-hosted-engine-setup asks if the installation is an upgrade and if so asks for the name of the currently used management bridge. Also the question about starting "engine-setup" could then be defaulting to "no".

Additional info: