block/022: skip test when only 1 cpu available

block/022: skip test when only 1 cpu available

Below is fail log in single cpu node.
block/022 (Test hang caused by freeze/unfreeze sequence)     [failed]
    runtime    ...  30.138s
    --- tests/block/022.out	2020-10-09 12:43:48.000000000 +0000
    +++ /usr/local/blktests/results/nodev/block/022.out.bad	2020-10-09 13:45:18.594417401 +0000
    @@ -1,2 +1,3 @@
     Running block/022
    +taskset: failed to set pid 13212's affinity: Invalid argument
     Test complete

Signed-off-by: Xiao Liang <xiliang@redhat.com>
[Shin'ichiro: fixed commit message typo and resolved merge conflict]
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>