Announce current state after clicking connect/disconnect buttons

Clearly indicate the current state is connecting or disconnecting after
clicking on the button for TalkBack users by setting the content
description respectively.

Flag: EXEMPT bugfix
Bug: 419160629
Test: manually test with TalkBack on, video attached in bug
Change-Id: Ic5c5dfe0065190427dd849a562cbc3204a7c4ece