OpTestPCI: force boot to petitboot/OS and get more meaninful diff
OpTestPCI: force boot to petitboot/OS and get more meaninful diff

We use /usr/bin/diff rather than python cmd(), this means we get a
more meaningful diff if there's a problem

We also now set IPMI boot devices to bios (petitboot) and disk (to boot OS)
so that we always end up in the right place

Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

open-power/op-test-framework,open-power/op-test-framework,open-power/op-test-framework