Fix connection time for GATT clients

Conenction time was not logged correctly in bluetooth_manager
dumpsys. Fix this by adding the wall clock time when connection
started and the elapsed time in ms for which the connection has
been active.

BUG: 65543218
Test: Tested with VR headset.
Change-Id: I756f3f807bd3e3c61cadc00567e367941bc3f021