[seahorse] Fix build with vala's stricter property checking

[Rico Tzschichholz <ricotz src gnome org>]

commit 7f64db1151ef95cdf2316c5ed34459d3076685d3
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Sat Mar 11 19:45:05 2017 +0100

    Fix build with vala's stricter property checking
    
    Workaround definition difference between`Seahorse.Place.label' and
    `Secret.Collection.label' property.

 common/place.vala        |    2 +-
 pkcs11/pkcs11-token.vala |    2 ++
 2 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/common/place.vala b/common/place.vala
index b807f52..ac925fe 100644
--- a/common/place.vala
+++ b/common/place.vala
@@ -21,7 +21,7 @@
 namespace Seahorse {
 
 public interface Place : Gcr.Collection {
-       public abstract string label { owned get; }
+       public abstract string label { owned get; set; }
        public abstract string description { owned get; }
        public abstract string uri { owned get; }
        public abstract GLib.Icon icon { owned get; }
diff --git a/pkcs11/pkcs11-token.vala b/pkcs11/pkcs11-token.vala
index d26e6b7..042381e 100644
--- a/pkcs11/pkcs11-token.vala
+++ b/pkcs11/pkcs11-token.vala
@@ -74,6 +74,8 @@ public class Token : GLib.Object, Gcr.Collection, Place, Lockable {
                                return C_("Label", "Unknown");
                        return token.label;
                }
+               set {
+               }
        }
 
        public string description {