KnifeMode, Message display, Reset cvar

[Rushaway]

• If KnifeMode is on, don't log the LogPlayerEvent damage_zombie bcs the DealDamage function deal 999999 damage and will trigger damage_zombie multiple time.
  https://github.com/srcdslab/sm-plugin-KnifeMode/blob/master/addons/sourcemod/scripting/KnifeMode.sp#L188

• When KnifeMode is unload, cvar sm_topdefenders_display_type doesn't get restored correctly

• On ZR_OnClientInfect the message code be easily improved