qemu-nbd: Permit --shared=0 for unlimited clients

This gives us better feature parity with QMP nbd-server-start, where
max-connections defaults to 0 for unlimited.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210209152759.209074-3-eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2 files changed