qemuDomainGetMachineName: Access embeddedRoot from driver rather than cfg
qemuDomainGetMachineName: Access embeddedRoot from driver rather than cfg

The cfg->root is going away, therefore get the info right from
the driver structure.

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>
Reviewed-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>
Reviewed-by: Daniel Henrique Barboza <627b089ad62deae9aaf06ccfa2c9056df28927e0@gmail.com>
Reviewed-by: Daniel P. Berrangé <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

jfehlig/libvirt,nertpinx/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,olafhering/libvirt,zippy2/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,olafhering/libvirt,zippy2/libvirt,crobinso/libvirt,olafhering/libvirt,jardasgit/libvirt,nertpinx/libvirt,nertpinx/libvirt,zippy2/libvirt,olafhering/libvirt,libvirt/libvirt,crobinso/libvirt,jardasgit/libvirt,zippy2/libvirt,libvirt/libvirt,crobinso/libvirt,jardasgit/libvirt,libvirt/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,crobinso/libvirt,nertpinx/libvirt,libvirt/libvirt,jfehlig/libvirt