[gnome-software] rpm-ostree: Add missing locking when creating DnfContext

[Kalev Lember <klember src gnome org>]

commit 13eca948e1d881082e9b226cad43ce3528e44121
Author: Kalev Lember <klember redhat com>
Date:   Tue May 12 10:18:43 2020 +0200

    rpm-ostree: Add missing locking when creating DnfContext
    
    Fixes https://gitlab.gnome.org/GNOME/gnome-software/issues/983

 plugins/rpm-ostree/gs-plugin-rpm-ostree.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/plugins/rpm-ostree/gs-plugin-rpm-ostree.c b/plugins/rpm-ostree/gs-plugin-rpm-ostree.c
index 3811f935..f2c33484 100644
--- a/plugins/rpm-ostree/gs-plugin-rpm-ostree.c
+++ b/plugins/rpm-ostree/gs-plugin-rpm-ostree.c
@@ -657,6 +657,9 @@ gs_plugin_refresh (GsPlugin *plugin,
                    GError **error)
 {
        GsPluginData *priv = gs_plugin_get_data (plugin);
+       g_autoptr(GMutexLocker) locker = NULL;
+
+       locker = g_mutex_locker_new (&priv->mutex);
 
        if (!ensure_rpmostree_dnf_context (plugin, cancellable, error))
                return FALSE;