Fix unexpected pairing failures after CTKD

Before:
1. Bond on LE Tranport, then use CTKD to generate Classic Keys.
2. Immediately establish BR/EDR connection.
3. Remote returns no SMP support in "Fixed Channels Supported".
4. L2CAP layer tells SMP BR module SMP channel is closed.
5. SMP BR module triggers pairing failure

After:
L2CAP layer is smart, knows to not pass the channel closed event when
SMP BR module is in IDLE state after CTKD.

Test: Bond using LE transport with device that does not support SMP on
      BR/EDR multiple times.
Bug: 296326447
Change-Id: I6b0b3f271dc21f15b3f9e483e366b24c139afc63