[asterisk-users] "CBAnn" channel not going away in Asterisk 12

[Richard Kenner]

After an upgrade to Asterisk 12, I'm "collecting" channels.  When I enter
and then exit a conference room, I see:

    -- <CBAnn/207-0000067f;1> Playing 'confbridge-leave.slin' (language 'en')
    -- Channel CBAnn/207-0000067f;2 joined 'softmix' base-bridge <5edb1920-3774-4ba3-8c4d-23e8fd04519c>
    -- Channel CBAnn/207-0000067f;2 left 'softmix' base-bridge <5edb1920-3774-4ba3-8c4d-23e8fd04519c>

I'd expect those channel to immediately go away, but they just stay around:

asterisk*CLI> core show channel CBAnn/207-0000067f;1
 -- General --
           Name: CBAnn/207-0000067f;1
           Type: CBAnn
       UniqueID: 1398809161.20186
       LinkedID: 1398809161.20186
      Caller ID: (N/A)
 Caller ID Name: (N/A)
Connected Line ID: (N/A)
Connected Line ID Name: (N/A)
Eff. Connected Line ID: (N/A)
Eff. Connected Line ID Name: (N/A)
    DNID Digits: (N/A)
       Language: en
          State: Up (6)
  NativeFormats: (nothing)
    WriteFormat: unknown
     ReadFormat: unknown
 WriteTranscode: No 
  ReadTranscode: No 
 Time to Hangup: 0
   Elapsed Time: 0h1m3s
      Bridge ID: (Not bridged)
 --   PBX   --
        Context: default
      Extension: s
       Priority: 1
     Call Group: 0
   Pickup Group: 0
    Application: (N/A)
           Data: (Empty)
 Call Identifer: (None)
      Variables:
[Apr 29 18:07:04] ERROR[21102]: cdr.c:3106 ast_cdr_serialize_variables: Unable to find CDR for channel CBAnn/207-0000067f;1

asterisk*CLI> core show channel CBAnn/207-0000067f;2
 -- General --
           Name: CBAnn/207-0000067f;2
           Type: CBAnn
       UniqueID: 1398809161.20187
       LinkedID: 1398809161.20186
      Caller ID: (N/A)
 Caller ID Name: (N/A)
Connected Line ID: (N/A)
Connected Line ID Name: (N/A)
Eff. Connected Line ID: (N/A)
Eff. Connected Line ID Name: (N/A)
    DNID Digits: (N/A)
       Language: en
          State: Up (6)
  NativeFormats: (slin)
    WriteFormat: slin
     ReadFormat: slin
 WriteTranscode: No 
  ReadTranscode: No 
 Time to Hangup: 0
   Elapsed Time: 0h3m30s
      Bridge ID: (Not bridged)
 --   PBX   --
        Context: default
      Extension: s
       Priority: 1
     Call Group: 0
   Pickup Group: 0
    Application: (N/A)
           Data: (Empty)
 Call Identifer: (None)
      Variables:
[Apr 29 18:09:31] ERROR[21102]: cdr.c:3106 ast_cdr_serialize_variables: Unable to find CDR for channel CBAnn/207-0000067f;2