crypto/tls: set CipherSuite for VerifyConnection

crypto/tls: set CipherSuite for VerifyConnection

The ConnectionState's CipherSuite was not set prior
to the VerifyConnection callback in TLS 1.2 servers,
both for full handshakes and resumptions.

Change-Id: Iab91783eff84d1b42ca09c8df08e07861e18da30
Reviewed-on: https://go-review.googlesource.com/c/go/+/236558
Run-TryBot: Katie Hockman <katie@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>