[PATCH v5 13/18] xen/pvcalls: implement release command

Release both active and passive sockets. For active sockets, make sure to avoid possible conflicts with the ioworker reading/writing to those sockets concurrently. Set map->release to let the ioworker know atomically that the socket will be released soon, then wait until the ioworker finishes

[PATCH v5 13/18] xen/pvcalls: implement release command

Release both active and passive sockets. For active sockets, make sure to avoid possible conflicts with the ioworker reading/writing to those sockets concurrently. Set map->release to let the ioworker know atomically that the socket will be released soon, then wait until the ioworker finishes