Mention global maintenance mode for self hosted installation

When following the Guide to do a minor update (RHV 4.3.x -> RHV 4.3.y) with a self hosted engine I have to enable the global maintenance mode. But I could not find any hint in the prereqs or the actual doc that I should do that.

I think this should be done by creating a corresponding part in the prereqs document. Something like "If you habe a self-hosted engine installed, please remember to enable global maintenance mode"

Best regards,
Eike