Cleanup lockscreen security settings

Since we moved lockscreen security settings to a separate fragment,
these changes we have initially made are not longer needed

Change-Id: Iac07850e974e9ea423fd8908ce1e134a9a2508ef
Remove 'More device settings' menu

Change-Id: I86cd84f6f6c408b26c04d92529e9a031c4fed1f7

Conflicts:
	res/xml/settings_headers.xml