You can SSH into your node and use the hosted-engine utility. To quote the documentation:

> To see all available commands, run hosted-engine --help. For additional information on a specific command, run hosted-engine --command --help.

There is also a section on "Booting the Engine Virtual Machine in Rescue Mode", see chapter 3.1.6 here: https://www.ovirt.org/documentation/administration_guide/index.html