dav: don't unescape the uri twice

path_equal tries to unescape path before comparing. Unfortunately
this function is used also for already unescaped paths. Therefore
unescaping can fail. This commit reverts changes which was done in
commit 50af53da and unescape just uris, which aren't unescaped yet.

https://bugzilla.gnome.org/show_bug.cgi?id=743298