s3: fix v2 signer on files with spaces - fixes #2438

Before this fix the v2 signer was failing for files with spaces in.

backend/s3/v2sign.go

@@ -44,16 +44,7 @@ func sign(AccessKey, SecretKey string, req *http.Request) {
 	req.Header.Set("Date", date)
 
 	// Sort out URI
-	uri := req.URL.Opaque
-	if uri != "" {
-		if strings.HasPrefix(uri, "//") {
-			// Strip off //host/uri
-			uri = "/" + strings.Join(strings.Split(uri, "/")[3:], "/")
-			req.URL.Opaque = uri // reset to plain URI otherwise Ceph gets confused
-		}
-	} else {
-		uri = req.URL.Path
-	}
+	uri := req.URL.EscapedPath()
 	if uri == "" {
 		uri = "/"
 	}