subrepo: fix normalizing paths with scheme
After revision 0afe96e374a7, subrepo paths were normalized using
posixpath.normpath and that resulted in ssh paths being wrongly converted
from ssh://host/path to ssh:/host/path
This fix applies the same logic used in urlutil.url to split the path scheme
from the rest and only use posixpath.normpath to the string after scheme://
edition = "2018"
max_width = 79
wrap_comments = true
error_on_line_overflow = true