qa/709 failing on Mac OS X - pmcollectl

[Ken McDonell <kenj@xxxxxxxxxxxxxxxx>]

There are no network.interface.in.compressed metrics from the darwin PMDA, 
leading to ...

! Traceback (most recent call last):
! File "/usr/local/bin/pmcollectl", line 9, in <module>
! ssx.print_line()
! File "/usr/local/bin/pmcollectl", line 9, in print_line
! self.print_verbose()
! File "/usr/local/bin/pmcollectl", line 9, in print_verbose
! sum(self.ss.get_metric_value('network.interface.in.compressed')),
! TypeError: 'int' object is not iterable

My questions are:

(a) should pmcollectl handle this case correctly?
(b) should qa/709 be _notrun for darwin (and other platforms where required 
metrics are unavailable)?