x/net/webdav: percent-encode D:href in the XML.

Fixes golang/go#13286

Change-Id: If1e727bc18c64232b82484d9e82063cc59bcc826
Reviewed-on: https://go-review.googlesource.com/16859
Reviewed-by: Robert Stepanek <robert.stepanek@gmail.com>
Reviewed-by: Nigel Tao <nigeltao@golang.org>
diff --git a/webdav/webdav.go b/webdav/webdav.go
index 82f8a90..af953ec 100644
--- a/webdav/webdav.go
+++ b/webdav/webdav.go
@@ -615,7 +615,7 @@
 
 func makePropstatResponse(href string, pstats []Propstat) *response {
 	resp := response{
-		Href:     []string{href},
+		Href:     []string{(&url.URL{Path: href}).EscapedPath()},
 		Propstat: make([]propstat, 0, len(pstats)),
 	}
 	for _, p := range pstats {