Bug #311560 --> Migration doesn't select any option by default

sr=bienvenu

mail/components/migration/content/migration.js

@@ -68,6 +68,8 @@ var MigrationWizard = {
       nothing.hidden = false;      
     }
 	
+    this.onImportSourcePageShow();
+	
     // Behavior alert! If we were given a migrator already, then we are going to perform migration
     // with that migrator, skip the wizard screen where we show all of the migration sources and 
     // jump right into migration.

mail/components/migration/content/migration.xul

@@ -58,7 +58,6 @@
   
   <wizardpage id="importSource" pageid="importSource" next="selectProfile"
               label="&importSource.title;"
-              onpageshow="MigrationWizard.onImportSourcePageShow();"
               onpageadvanced="MigrationWizard.onImportSourcePageAdvanced();">
 #ifdef XP_WIN
     <description>&importFrom.label;</description>