conf: Move virDomainGenerateMachineName to hypervisor/

conf: Move virDomainGenerateMachineName to hypervisor/

The virDomainGenerateMachineName() function doesn't belong in
src/conf/ really, because it has nothing to do with domain XML
parsing. It landed there because of lack of better place in the
past. But now that we have src/hypervisor/ the function should
live there. At the same time, the function name is changed to
match new location.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>