cman: fix printing of error if clustername is too long
    
    Patch 03e9af7db105 did mask an error and was not propagating the
    error string in the cman pipe, making it impossible to see the error
    at startup when it is more important, since clustername cannot be changed
    at runtime.
    
    Resolves: rhbz#728230
    
    Signed-off-by: Christine Caulfield <ccaulfie@redhat.com>
    Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>