Fix bug in resource mgr round robin function.

Fixing bug where function did not add acquired allocation objects to the
assembled collection of such objects, and thus only an empty list was
returned.

python/lib/scheduler/dmod/scheduler/resources/resource_manager.py

@@ -362,4 +362,5 @@ def allocate_round_robin(self, cpus: int, memory: int,
                 if not isinstance(alloc, ResourceAllocation):
                     self.release_resources(allocations)
                     return [None]
+                allocations.append(alloc)
         return allocations