avatar: fix black camera image

On some systems, when opening the camera to take a new picture for
the avatar, the result is a black image. The log also outputs
"bad dawable". It seems the VideoWidget doesn't like being a page
directly in a GtkStack. Instead we put it in a GtkFrame which does
not get destroyed. This seems to fix the issue.

Change-Id: Ia3796ad3b3f02947619c2b0ba57ad4b54e30552e
Tuleap: #840
diff --git a/ui/avatarmanipulation.ui b/ui/avatarmanipulation.ui
index f54e7f5..741a319 100644
--- a/ui/avatarmanipulation.ui
+++ b/ui/avatarmanipulation.ui
@@ -33,26 +33,31 @@
     <child>
       <object class="GtkBox" id="box_views_and_controls">
         <property name="visible">True</property>
-        <property name="can_focus">False</property>
         <property name="orientation">vertical</property>
         <property name="spacing">5</property>
         <child>
           <object class="GtkStack" id="stack_views">
             <property name="visible">True</property>
-            <property name="can_focus">False</property>
             <child>
               <object class="GtkImage" id="image_avatar">
                 <property name="visible">True</property>
-                <property name="can_focus">False</property>
               </object>
               <packing>
                 <property name="name">page_avatar</property>
               </packing>
             </child>
             <child>
+              <object class="GtkFrame" id="frame_video">
+                <property name="visible">True</property>
+                <property name="shadow-type">GTK_SHADOW_NONE</property>
+              </object>
+              <packing>
+                <property name="name">page_photobooth</property>
+              </packing>
+            </child>
+            <child>
               <object class="GtkBox" id="vbox_selector">
                 <property name="visible">True</property>
-                <property name="can_focus">False</property>
                 <property name="orientation">vertical</property>
                 <property name="valign">center</property>
                 <property name="halign">center</property>