Show keypad while setting PIN in setup wizard

Currently The activity not requesting showSoftInput() and hence keypad
doesn't show up.
Activity.onResume(), we should call ImeAwareEditText.scheduleSoftInput()
to request schedule ShowSoftInput() when EditText gains focus.

Fixes: 63582564
Test: Manually launch com.google.android.setupwizard/.SetupWizardTestActivity

Change-Id: Ib75ba0f361b8b46c3b717cc1ffb864726958ed82