nbdx_server: fix coverity issue

Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
nbdx_server: fix segmentation fault in nbdx_handler_free_portal_data

Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
nbdx_server: api fix

Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
nbdx_server: removed usage of deprecated xio_get_connection function

Also return error when fail to process request.

Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
nbdx: free nbdx_session in error flow

Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
nbdx_server: remove redundant xio_msg from nbdx_io_portal_data

Signed-off-by: Max Gurtovoy <maxg@mellanox.com>