Disable Start ops untill KillAll finishes
StartApp/RestartApp/StartPlan/RestartPlan actions disabled on GUI when in the middle of KillAll operation.
Prevent the user from starting apps while some are still being killed (especially with SoftKill=1 the killing may take more time).
Hardcoded timeout 10secs for re-enabling the buttons if killing takes too long to avoid blocking the Dirigent completely.