pmdaprometheus: Fix metadata generator to handle instances which has space in it's value
pmdaprometheus: Fix metadata generator to handle instances which has space in it's value

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