grains: Remove dmesg path and add additional detection path for virtualbox, rhev, ovirt, and gce
grains: Remove dmesg path and add additional detection path for virtualbox, rhev, ovirt, and gce

Improves behavior mentioned in #25101.

dmesg has a limited buffer size and will eventually drop the lines we are trying to match against. This patch removes calling dmesg and adds an additional detection path.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt