client.c: Removed server error verification (error 6)

This error is not necessary anymore, because the server will print the
appropriate error message, exiting with error 5 in these cases.

Signed-off-by: Erik Alexandre Pucci <eap08@c3sl.ufpr.br>
Acked-by: Josiney de Souza <josineys@c3sl.ufpr.br>
Signed-off-by: Danilo K. S. Yorinori <danilok@c3sl.ufpr.br>