Add except 'AttributeError' on Connection.close
Add except 'AttributeError' on Connection.close

Fix #466

erickvermot/kytos,kytos/kyco,diraol/kytos,diraol/kytos,cemsbr/kytos,macartur/kytos,cemsbr/kytos,diraol/kytos,erickvermot/kytos,renanrodrigo/kytos,kytos/kytos,cemsbr/kytos,erickvermot/kytos