Add mx to homeserverInput

Author: SimonBrandner

src/components/views/dialogs/ServerPickerDialog.tsx

@@ -217,7 +217,7 @@ export default class ServerPickerDialog extends React.PureComponent<IProps, ISta
                         value={this.state.otherHomeserver}
                         validateOnChange={false}
                         validateOnFocus={false}
-                        id="homeserverInput"
+                        id="mx_homeserverInput"
                     />
                 </StyledRadioButton>
                 <p>