buffet: Make TLS shut down gracefully on connection termination

Perform simple unidirectional shutdown of TLS connection when we are
disconnecting from a server. There is no need to wait for the server
response since we are closing the underlying socket anyway.

Added more informational logging for XMPP connection start/teardown.

BUG=brillo:1155
TEST=`FEATURES=test emerge-link libchromeos buffet`

Change-Id: I118e0fbb33073d71583c9874deceac2d38565ec6
Reviewed-on: https://chromium-review.googlesource.com/275028
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Vitaly Buka <vitalybuka@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
1 file changed