Set job as shared when not exclusive on WCOSS2

WCOSS2 defaults to exclusive when it is not specified as
either exclusive (place=exclhost) or shared (place=shared).
Now set shared when job should be shared.

Refs NOAA-EMC#2135

workflow/rocoto/tasks.py

@@ -153,8 +153,11 @@ def get_resource(self, task_name):
         native = None
         if scheduler in ['pbspro']:
             native = '-l debug=true,place=vscatter'
+            # Set either exclusive or shared - default on WCOSS2 is exclusive when not set
             if task_config.get('is_exclusive', False):
                 native += ':exclhost'
+            else:
+                native += ':shared'
         elif scheduler in ['slurm']:
             native = '--export=NONE'