dbug log: verbosely detach conn<->lchan

When reading the log of OS#3686, I wished for explicit logging of when exactly
an lchan disassociates from a conn. Here is the debug logging I would have
liked to see.

I'm not sure whether we really need to merge this patch...

Change-Id: I97558b899e7f2578ba98287e7352dc072d02ce44
2 files changed