Disabling haptics in the system settings only affects Unity8 and a few system apps

How to reproduce:

1) Uncheck "Other vibrations" in System Settings > Sound
2) Open the dialer and press a few buttons
3) You will notice that the phone does not vibrate when pressing a button
4) Now open the clock app and press a few buttons
5) The selection in the system settings does not seem to affect the clock app and the phone still vibrates when pressing an AbstractButton or a derived item

Components to which the setting does apply:

* Unity 8
* System Settings
* Dialer
* Messaging app
* Address book

Components to which it does NOT apply:

* Webbrowser
* Camera
* Clock
* Terminal app
* File manager
* Document viewer
* Any click app from the store which I have tried so far

Debugging efforts so far:

I have added a few console.log() calls and saw that in Haptics.qml, when the play() method is called, vibra.otherVibrate is true. So it seems as if the ServiceProperties object fails to fetch the proper value when running the aforementioned apps.

A few observations:

* All apps for which it works are legacy (e.g. non-click) applications.
* However, the webbrowser app is a legacy one, too, but it doesn't work there.
* All apps for which it works run unconfined.
* However, the terminal and the file manager apps are unconfined, too.
* The apps for which it works seem to use the most recent UITK version.
* However, the document viewer does that as well.

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phablet@ubuntu-phablet:~$ system-image-cli -i
current build number: 218
device name: mako
channel: ubuntu-touch/rc-proposed/bq-aquaris.en
last update: 2016-01-21 23:18:06
version version: 218
version ubuntu: 20160121.2
version device: 20160112
version custom: mako-1.1