OSDMonitor: enable getting hit set parameters
We would like to get the hit set parameters: hit_set_type |
hit_set_period | hit_set_count | hit_set_fpp via OSDMonitor

Signed-off-by: Kai Zhang <zakir.exe@gmail.com>
Merge pull request #1334 from kazhang/wip-get-hit_set-parameter

OSDMonitor: enable getting hit set parameters

Reviewed-by: Sage Weil <sage@inktank.com>