block: fix fio jobs for 027 and add cgroup support

block: fix fio jobs for 027 and add cgroup support

Previously, the test was broken as "$fio_jobs" was considered as a
string instead of additional parameters. This is fixed here.

Second, there was an issue with earlier kernels when request lists
existed such that request_queues were never being cleaned up because
non-root blkgs took a reference on the queue. However, blkgs were being
cleaned up after the last reference to the request_queue was put back.
This creates a blktest cgroup for the fio jobs to utilize and should be
useful for catching this scenario in the future.

Signed-off-by: Dennis Zhou <dennis@kernel.org>