nfssvc: When the client disconnects, close the socket before sleeping.

nfssvc: When the client disconnects, close the socket before sleeping.

If the server doesn't close the socket immediately and starts waiting
for the client to reconnect, then the TCP connection will remain open.
The client will have to wait for the connection to be closed in order
to reconnect with the same source port; this never happens, resulting
in a freeze until the file system is umounted.

This change fixes Linux NFS clients freezing after 5 min of inactivity.

ok miod, help from claudio