BAS: Write CCCD to get notified battery level

Tag: #feature
Bug: 233692672
Test: Manually connect to LE device and wait to
see the battey level drops.

Merged-In: Ib610bddcb69d01710dfcc1d5c375dc4ba4d3b912
Change-Id: Ib610bddcb69d01710dfcc1d5c375dc4ba4d3b912
(cherry picked from commit e14fcef8)