test: Fix playlist plugin path handling for Windows compatibility
test: Fix playlist plugin path handling for Windows compatibility

sampsyo/beets,shamangeorge/beets,sampsyo/beets,beetbox/beets,beetbox/beets,sampsyo/beets,jackwilsdon/beets,SusannaMaria/beets,jackwilsdon/beets,shamangeorge/beets,SusannaMaria/beets,shamangeorge/beets,ibmibmibm/beets,ibmibmibm/beets,jackwilsdon/beets,ibmibmibm/beets,shamangeorge/beets,beetbox/beets,beetbox/beets,jackwilsdon/beets,ibmibmibm/beets,sampsyo/beets,SusannaMaria/beets,SusannaMaria/beets