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.
Add missing space
Merge pull request #1044 from ronawho/fix-pbs-aprun-mpp

Update pbs-aprun launcher to use place/select for pbspro

[reviewed by @thomasvandoren]

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.