Dont disconnect if connection complete event with an ACL connection exists

When create connection and connect request from the same device happen
at the same time, the first connection complete event will work as
expected and set link state to LST_CONNECTED.
But the second connection complete event will disconnect the exist
connection due to the link state is LST_CONNECTED and status is
HCI_ERR_CONNECTION_EXISTS.

Bug: 141872633
Test: Create connection and receive connect request at the same time.
      Check if connection work as expected.

Change-Id: Ibefa1021c3d314522a62cae0b1a31a34b0f8dbc8