INSTANCES_SPEC_ARGUMENT client option does not validate instance range

An of order instance range (e.g. "/10-2") results in empty list of instances. In case of a scheduler updater this leads to updating the entire job instead of specific instances.

The offending line: https://github.com/apache/aurora/blob/439a168f9cdd6fe58a12009b51bedad4ac152948/src/main/python/apache/aurora/client/cli/options.py#L74