Created Unassigned: Duplicate accelerator keys does not toggle when a control is after an xceed UpDown [22140]

Scenario:

In Wpf when there are duplicate accelerator/mnemonic keys in a window then the focus toggles between the controls. Example the accelerator key below is Alt+P and the same for two textboxes. Pressing Alt+p toggles the focus on the two textbox.

```
<Label Content="_Product" Target="{Binding ElementName=_txtA}"/>
<TextBox Name="_txtA"/>

<Label Content="_Product" Target="{Binding ElementName=_txtB}"/>
<TextBox Name="_txtB"/>
```

* When there is an xceed updown control this toggling does not work __IF__ the control with the same accelerator key is __AFTER__ the updown (see attachment). In summary the code is below:

```
<Label Content="_Product" Target="{Binding ElementName=_updown}"/>
<xceed:IntegerUpDown AllowSpin="False" ShowButtonSpinner="False" Name="_updown"/>

<!--Accelerator keys DOES NOT work when textbox is after updown control-->
<Label Content="_Product" Target="{Binding ElementName=_txtB}"/>
<TextBox Name="_txtB"/>
```



Accelerator keys work __IF__ the control with the same accelerator key is __BEFORE__ the updown (see attachment). In summary the code is below:

```
<!--Accelerator keys work when textbox is before updown control-->
<Label Content="_Product" Target="{Binding ElementName=_txtA}"/>
<TextBox Name="_txtA"/>

<Label Content="_Product" Target="{Binding ElementName=_updown}"/>
<xceed:IntegerUpDown AllowSpin="False" ShowButtonSpinner="False" Name="_updown"/>
```