covering proximity sensor turns screen black when headset is plugged or phone speaker is on

Enviroment:

current build number: 443
device name: krillin
channel: ubuntu-touch/rc-proposed/bq-aquaris.en
last update: 2016-10-05 16:36:32
version version: 443
version ubuntu: 20161005
version device: 20160606-ab415b2
version custom: 20160831-991-38-18

Preconditions: have headset to plug

Steps to reproduce:

 1 Make a call from Ubuntu Phone
 2 After call is connected, put phone up to ear
 3 Verify the screen goes black
 4 Now plug in a headset
 5 Verify that moving phone up to ear does not cause the screen to go black
 7 Unplug headset
 10 Now enable speakerphone
 11 Verify that the screen does not go black when move the phone up to ear

Current result:in 5 & 11 screen goes black due to headset or speaker

Expected result: in 5 & 11 screen should not turn black

Add info: time stamp 16:09