Downgrade "There was no default identity" warning to debug

This happens on first run of kontact, no point in worrying the user.

src/identitymanager.cpp

@@ -150,7 +150,7 @@ void IdentityManager::Private::readConfig(KConfig *config)
             mIdentities << Identity();
         }
 
-        qCWarning(KIDENTITYMANAGEMENT_LOG) << "IdentityManager: There was no default identity."
+        qCDebug(KIDENTITYMANAGEMENT_LOG) << "IdentityManager: There was no default identity."
                                          << "Marking first one as default.";
         mIdentities.first().setIsDefault(true);
     }