qa: handle missing zswap metrics return code in qa/999 checks
qa: handle missing zswap metrics return code in qa/999 checks

edwardt/pcp,prasincs/pcp,aeg-aeg/pcpfans,tjanez/pcp,aeg-aeg/pcpfans,edwardt/pcp,aeg-aeg/pcpfans,aeg-aeg/pcpfans,aeg-aeg/pcpfans,prasincs/pcp,tjanez/pcp,aeg-aeg/pcpfans,adfernandes/pcp,adfernandes/pcp,edwardt/pcp,edwardt/pcp,prasincs/pcp,andyvand/cygpcpfans,prasincs/pcp,adfernandes/pcp,edwardt/pcp,wuliming/pcp,tjanez/pcp,andyvand/cygpcpfans,wuliming/pcp,wuliming/pcp,tjanez/pcp,adfernandes/pcp,edwardt/pcp,andyvand/cygpcpfans,wuliming/pcp,andyvand/cygpcpfans,tjanez/pcp,aeg-aeg/pcpfans,tjanez/pcp,adfernandes/pcp,wuliming/pcp,prasincs/pcp,adfernandes/pcp,wuliming/pcp,edwardt/pcp,prasincs/pcp,aeg-aeg/pcpfans,wuliming/pcp,prasincs/pcp,andyvand/cygpcpfans,tjanez/pcp,prasincs/pcp,wuliming/pcp,andyvand/cygpcpfans,edwardt/pcp,adfernandes/pcp,adfernandes/pcp,tjanez/pcp,andyvand/cygpcpfans,andyvand/cygpcpfans