adding dmesg to list of tools to that determine the virtual grains

I added dmesg as a command to check for virtual grains.

The goal was to remove dependency on another package/external tools and use one that should be available on all systems.

Tested on
Fedora 17 on Virtualbox 4.2.10
Centos 6.0 on Virtualbox 4.2.10
Fedora 17 on Virtual PC
Centos 6.3 on Virtual PC

I don't have Qemu/kvm or Parallels to test this on.