Don't send HCI disconnect repeatedly

It is possible for the host stack to send multiple HCI disconnect
commands for the same handle within a short time. Prevent such a
scenario by checking whether we have initiated disconnection for that
handle or not.

Bug: 374039861
Bug: 381175628
Test: m -j
Flag: com.android.bluetooth.flags.dont_send_hci_disconnect_repeatedly

Change-Id: I16900e883488eec0eaef3894168a2e4ec0b69b20