Clearing threshold states via shell should take effect immediately and not require restart

The shell commands for clearing threshold states in https://github.com/OpenNMS/opennms/pull/2690 only affect the state stored in the KV store. Usually thresholding will be using the in-memory copy of the state and that copy will not be cleared when the command is run. The net effect of this is that thresholding would need to be restarted in order to see that the state was cleared.

The clear and clear-all commands should be updated so that when they are ran they also clear the in memory states effected immediately.