Add bug fixes in vendor classes

1. Remove final declaration for VendorDcTracker
2. Update isPhoneInVoiceCall method for VendorPhoneSwitcher
3. Make constructor protected for VendorSubscriptionInfoUpdater

Test: TH
Change-Id: I8790f4f4f2062a5e15d1a1195f3129c07c7a09b4
Bug: 157726600
(cherry picked from commit 58da7215c9246ef335b1deee2503191bc65c7c33)