Revert "test/vhost: lower fio job iodepth"

Now that the bdev layer handles ENOMEM errors internally, we can restore
the original fio queue depths that were reduced to avoid test pool
failures.

This reverts commit 26a40ff9.

Change-Id: Ib7f1bd1e0251f4b2a6370cfd84e2f60e8ee15428
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-on: https://review.gerrithub.io/380855


Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>