tcptls: Bad file descriptor error when reloading chan_sip

While running through some scenarios using chan_sip and tcp a problem would
occur that resulted in a flood of bad file descriptor messages on the cli:

tcptls.c:712 ast_tcptls_server_root: Accept failed: Bad file descriptor

The message is received because the underlying socket has been closed, so is
valid. This is probably happening because unloading of chan_sip is not atomic.
That however is outside the scope of this patch. This patch simply stops the
logging of multiple occurrences of that message.

ASTERISK-24728 #close
Reported by: Thomas Thompson
Review: https://reviewboard.asterisk.org/r/4380/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@431218 65c4cc65-6c06-0410-ace0-fbb531ad65f3