Add test for Connection.shutdown on closed socket
Add test for Connection.shutdown on closed socket

sorenh/pyopenssl,hynek/pyopenssl,mhils/pyopenssl,r0ro/pyopenssl,sholsapp/pyopenssl,mitghi/pyopenssl,mschmo/pyopenssl,aalba6675/pyopenssl,adamwolf/pyopenssl,elitest/pyopenssl,daodaoliang/pyopenssl,reaperhulk/pyopenssl,mhils/pyopenssl,samv/pyopenssl,kjav/pyopenssl,mitghi/pyopenssl,aalba6675/pyopenssl,r0ro/pyopenssl,hynek/pyopenssl,pyca/pyopenssl,reaperhulk/pyopenssl