rng-tools: inhibit update-rc.d when not using sysvinit

Signed-off-by: Fahad Usman <fahad_usman@mentor.com>
libvirt: inhibit update-rc.d when not using sysvinit

Signed-off-by: Fahad Usman <fahad_usman@mentor.com>
Merge pull request #325 from fahadusman/SB-3431

inhibit update-rcd.bbclass when not using sysvinit