Fix initial focus in LockScreenUi

SessionManagementScreen is a FocusScope and needs focus explicitly assigned
to it. If inside a QQC2 StackView this is taken care of, but for some reason
in a QQC1 StackView this isn't the case for the initial item. Do it explicitly.


(cherry picked from commit a66dcbdda7)

lookandfeel/contents/lockscreen/LockScreenUi.qml

@@ -230,6 +230,9 @@ PlasmaCore.ColorScope {
                 id: mainBlock
                 lockScreenUiVisible: lockScreenRoot.uiVisible
 
+                // This is a focus scope and QQC1 StackView (unlike QQC2) does not set focus to the current item
+                focus: true
+
                 showUserList: userList.y + mainStack.y > 0
 
                 Stack.onStatusChanged: {