What helped in my situation:
service mgmt-vmware restart
on the service console
Official KB for this situation:
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1028351
ESX/ESXi host in vCenter Server reports the error: Unable to apply DRS resource settings on host. The operation is not allowed in the current state
