Ignore drag action on the switch button of MasterSwitchPreference

MasterSwitchPreference provides a toggle switch and it only
acts for clicking events. This fix consumes move events to
ignore drag actions.

Bug: 148770615
Test: make RunSettingsRoboTests ROBOTEST_FILTER=MasterSwitchPreferenceTest
      Manually drag the switch button of MasterSwitchPreference and
      observe the switch state is not changed.
Change-Id: I0d8b947b32d35b85403fc65605c18c09a4053135