nvmeof-mp/012, srp/012: fix the scheduler list

nvmeof-mp/012, srp/012: fix the scheduler list

There is no cfq scheduler and new added kyber scheduler in lastest kernel,
introduce get_scheduler_list and fix nvmeof-mp/012 srp/012

To reproduce it:
$ ./check nvmeof-mp/012
nvmeof-mp/012 (dm-mpath on top of multiple I/O schedulers)   [passed]
    runtime  5.922s  ...  8.804s

$ cat results/nodev/nvmeof-mp/012.full  | grep -n "Changing scheduler"
31:Changing scheduler of dm-3 from mq-deadline kyber [bfq] none into cfq failed
47:Changing scheduler of dm-3 from mq-deadline kyber [bfq] none into cfq failed

Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Yi Zhang <yi.zhang@redhat.com>