[Improvement] clean the completed jobs

[ldming]

Is your improvement request related to a problem? Please describe.

When the bench completed, clean the generated jobs.

➜  ~ kbcli bench list
NAME     NAMESPACE   KIND       STATUS     COMPLETIONS
mypg     default     Pgbench    Complete   3/3
mytest   default     Sysbench   Complete   3/3

➜  ~ k get jobs
NAME                                                       COMPLETIONS   DURATION   AGE
mypg-cleanup                                               1/1           5s         22m
mypg-prepare                                               1/1           6s         22m
mypg-run-0                                                 1/1           64s        22m
mytest-cleanup                                             1/1           62s        40m
mytest-prepare                                             1/1           12s        39m
mytest-run-0                                               1/1           96s        39m