Handle net_ticktime argument specially. Resolves RIAK-1281

`escript` does not process emulator/runtime arguments like `erl`, so you can't
blindly pass an application environment setting on the command line. This
meant that the `-kernel net_ticktime N` argument passed to nodetool was not
functioning as intended and being treated as regular arguments, resulting in a
crash.

The net_ticktime setting is also a sensitive setting and should likely be set
before the Erlang distribution is started. I can only assume that the original
author that added it had intended for it to be loaded by the
application_controller, as `erl` does.

Therefore, this change handles net_ticktime specially in 
nodetool:process_args/3 and puts it as the first argument to the script so
that it is set first.