Hypervisor name C++ API

Convert the RESTful API hypervisor name translation function into an OSv
C++ API that can be used elsewhere as well.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
monitoring-agent: Fix hypervisor name confusion

The code uses firmware vendor as the hypervisor name...

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>