HAP: wait for MTU to process reconnection event

When HAP reconnect, it sends indication of all events that happen during
the disconnection.
But it should wait for the profile to be ready and for the MTU to have
been negotiated or else the remote may not be ready yet.

As a side effect of this, the current GattServer doesn't re-populate the
handle of subscriber during a reconnection, we have to bypass this check
to send the notification

tests/hap_test.py

@@ -82,7 +82,6 @@ async def hap_client():
     )
 
     await devices.setup_connection()
-    # TODO negotiate MTU > 49 to not truncate preset names
 
     # Mock encryption.
     devices.connections[0].encryption = 1  # type: ignore
@@ -93,6 +92,9 @@ async def hap_client():
     )
 
     peer = device.Peer(devices.connections[1])  # type: ignore
+    await peer.request_mtu(49)
+    peer2 = device.Peer(devices.connections[0])  # type: ignore
+    await peer2.request_mtu(49)
     hap_client = await peer.discover_service_and_create_proxy(
         hap.HearingAccessServiceProxy
     )