The librbdfio benchmark creates RBDs using node names specified in the job file. However, the clients try to access the RBDs using their own "hostname -s" name. If the names are not the same then tests will fail, with output like this in the output files:
Starting 1 process
rbd engine: RBD version: 0.1.9
rbd_open failed.
fio_rbd_connect failed.
I will be submitting a fix.