Close kombu.connection.BrokerConnection correctly

Make kombu.connection.BrokerConnection use release() to close the connection.
It has no such attribute as close(), since AttributeError is in
connection_errors, the fault was previous concealed by the following catch
statement.

Change-Id: I9f7da2c64f9d408aa2a9ddf723ea83291887cff6
Merge "Close kombu.connection.BrokerConnection correctly"