pmdaprometheus: tolerate space after comma in label name format
pmdaprometheus: tolerate space after comma in label name format

plus minor pylint tweak

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