qa: resolve pmwebd -I-induced regression in test qa/661
qa: resolve pmwebd -I-induced regression in test qa/661

Seeing pmwebd test 661 failure on all Red Hat QE hosts, git
bisect finds it to be a regression from e9262b89b0fe where
a -I was added into pmwebd test options.  This changes the
way the -A option is handled, and is causing the two metric
regex parts of the test to no longer match on their archive
name components, so curl ends up producing no output.

While in there, also fix a small race where pid might not be
set by the time _cleanup is called, causing kill invocation
on an empty $pid.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp