Optimize tiles management

Don't allow re-adding same tiles

Change-Id: Ia887eaf250117797de2001b0ca3232ec7b370f78

https://github.com/camcory/android_packages_apps_Settings/commit/25d7acb9dac4650ad416cae6ad911e801670a23b

	modified:   src/com/android/settings/cyanogenmod/QuickSettingsTiles.java
	modified:   src/com/android/settings/cyanogenmod/QuickSettingsUtil.java