Fix copy/paste error in unit test (mg_get_cookie returns length)
Fix copy/paste error in unit test (mg_get_cookie returns length)

GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver,GerHobbelt/civet-webserver