Fix failure test cases in AccessibilityShortcutPreferenceFragmentTest

Root Cause: The lifecycle for
AccessibilityShortcutPreferenceFragmentTest did not be called correctly.

Solution:
* Call onAttach() before onCreate() to set some configs correctly, e.g.
FeatureFactory.
* Use ShadowFragment.class that we usually do in accessibility
tests.

Fix: 200906425
Fix: 201020915
Test: atest AccessibilityShortcutPreferenceFragmentTest
Change-Id: I3391c0a4a2c7c361a44c7d282b1d5d3e75a28a39
Merged-In: I3391c0a4a2c7c361a44c7d282b1d5d3e75a28a39