Disconnect Gatt during failure of service changed discovery process

Gatt service changed discovery holds link till it completes discovery of service,
characteristics, descriptots and writing notification for characteristic descriptor,
this change takes care of removing  the link if service discovery fails during any
stage of this process.

Bug: 21896912
Change-Id: Ie97a039568fedc66403895e7e917e4d72a5419e1