core: Fixed log for cluster unsupported emulated machine

When a cluster upgrade occurred and a host didn't support the new
cluster requirement, the error that was given included the cluster
old emulated machine value (which the host did support).
Error printout logic was fixed and messages changed accordingly.

Change-Id: I8397cd64364c98aa76818613dbe78ddef2391027
Bug-Url: https://bugzilla.redhat.com/1141508
Signed-off-by: Eldan Shachar <eshachar@redhat.com>