this might be worth a look, as can be seen in this bugreport, this message might be caused by differences between the CPU’s in your cluster. In the example posted there, the “monitor” flag is only present on the first core of a CPU.
EDIT: forgot to post the link: https://bugzilla.redhat.com/show_bug.cgi?id=873926
Can you check if you see something similar in the CPU model you use?
Check if you see any differences in the features of your cores by using:
“cat /proc/cpuinfo” on your virtualization servers.