Send connected callback immediately when attempting to connect to already connected device

Instead of adding the device to the connection manager, just send the
successfull connection callback.

This patch is restoring behaviour from before Connection Manager
refactor. During the refactor this behaviour was broken.

Bug: 130273570
Test: sl4a GattConnectTest
Change-Id: Ic4fa7089a8262f6f792206496a7cfb9c83a16eb2
Merged-In: Ic4fa7089a8262f6f792206496a7cfb9c83a16eb2