bnc#836363 - applying xen proposal fails after moving away from kvm
bnc#836372 - can not switch compute nodes from xen to kvm
only require certificate files for controllers (bnc#851514)
Merge pull request #256 from jsuchome/release/pebbles/master

bnc#836363 - applying xen proposal fails after moving away from kvm
Merge pull request #285 from jsuchome/cert-files

only require certificate files for controllers (bnc#851514)