Rename the used SSH key

Because of "If the default insecure keypair is used, Vagrant will
automatically replace it with a randomly generated keypair on first
vagrant up. [GH-2608]" it is necessary to rename the used SSH key
because it will be overwritten at the moment.

Change-Id: If9ee3860c93fe7b0c825ba8403ae3e25647266f3
Merge "Rename the used SSH key"