connection: close metadata_fd on connection close
connection: close metadata_fd on connection close

It's theoretically possible to leak an fd here in the case that we close
the connection before we send any message to cockpit-ws.  Clean that up.

martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,mvollmer/cockpit,martinpitt/cockpit,mvollmer/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit