librbdfio fails when client's hostname differs from identifier in CBT job file

[ASBishop]

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.