[2/2] Telephony: allow disabling call end sound

Also remove the category around the intrusive
incall settings since more settings are added
below and this looks then strange

PS7
correct defaultValue

Change-Id: I37477582ecb3a8b74eb80db351401d83aab92b82

Patchset: 7
https://gerrit.omnirom.org/#/c/3647/