Bluetooth: Fix Read Multiple Characteristics Values error response

According to Core Specification "An Error Response shall be sent by
the server in response to the Read Multiple Request if insufficient
authentication, insufficient authorization, insufficient encryption
key size is used by the client, or if a read operation is not permitted
on any of the Characteristic Values. The Error Code parameter is set as
specified in the Attribute Protocol."

If any handle used by client is invalid we should return and error.

Change-Id: I5489ce6284531822676a63edf13db23289866102
Signed-off-by: Szymon Janc <ext.szymon.janc@tieto.com>