Remove un-implemented Admin API methods.

Admin methods

setRuntimeProperty - is not implemented, and signature may be not sufficient to implement in the future. Remove this and add when feature is required.

getWorkManagerStats(String identifier) - since there is going to be single Teiid engine in a given VM, there is no need for the "identifier" parameter, this needs to be removed for simplicity.

getProcesses(String processIdentifier) - this method is not also implemented, it was kept to make "AdminApiServerDiscovery" supported. However the way it is currently it is not functional, either this needs to be removed or fixed for correct usage.