rsocket; Set POLLERR bit in revent in case of rs_connect_error

rsocket; Set POLLERR bit in revent in case of rs_connect_error

In non-blocking mode, on server side accept returns a new data
socket and select/poll should indicate when the socket is ready
for reading/writing.

This fix allows an application to receive an error in case of
connection failure.

Signed-off-by: Sasha Kotchubievsky <sashakot@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>
Signed-off-by: Sean Hefty <sean.hefty@intel.com>