vsock: send SIGPIPE on write to shutdowned socket

POSIX requires to send SIGPIPE on write to SOCK_STREAM socket which was
shutdowned with SHUT_WR flag or its peer was shutdowned with SHUT_RD
flag. Also we must not send SIGPIPE if MSG_NOSIGNAL flag is set.

Signed-off-by: Arseniy Krasnov <avkrasnov@salutedevices.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>