Update pbs-aprun launcher to use place/select for pbspro

The mpp* options have been deprecated (but still functional) for a while. Many
systems are completely disabling the mpp* options so we need to adjust to use
the place/select options for pbspro. For moab/torque we already used a different
set of options to request resources.
Just for code clarity. The snprintf's are just building up a string for the expect (ughh) script. It wouldn't change the string that's generated if it was on the same line, but it seemed clearer to me this way.