Calling SSL_shutdown while in init previously gave a "1" response,
meaning everything was successfully closed down (even though it
wasn't). Better is to send our close_notify, but fail when trying to
receive one.
The problem with doing a shutdown while in the middle of a handshake
is that once our close_notify is sent we shouldn't really do anything
else (including process handshake/CCS messages) until we've received a
close_notify back from the peer. However the peer might send a CCS
before acting on our close_notify - so we won't be able to read it
because we're not acting on CCS messages!
(Imported from upstream's f73c737c7ac908c5d6407c419769123392a3b0a9)
Change-Id: Iaad5c5e38983456d3697c955522a89919628024b
Reviewed-on: https://boringssl-review.googlesource.com/7207
Reviewed-by: David Benjamin <davidben@google.com>
b9824e2417