population of fio files should use fio_cmd provided in yaml

In using kvmrbdfio.py to run fio on my openstack guests, the population of the fio files does not use the path to the fio executable (fio_cmd) provided in the yaml file. I define the fio command path ...

----------- yaml excerpt -----------
benchmarks:
kvmrbdfio:
fio_cmd: "/usr/local/bin/fio"
----------- end excerpt ------------

... however the populate call instead uses no path and relies on the fio executable being in the $PATH defined by sudo users, which excludes /usr/local/bin where my fio resides, resulting in the population failing on the target systems.