Update settings.

Updates a set of agent settings.

             If the argument "key" has the value "policy": updates the global agent settings.
               - See  for agent setting names and values.
               - Zero or more of such settings can be specified.
                 - If a setting isn't specified, its previous value is deleted. The corresponding default
                   value will take the place of the previous value on the next call to
               - See  for restrictions on the values of the
                 - If at least one value is invalid, the entire set of settings is discarded.