daemonStreamHandleRead: Rework to follow our coding pattern
    
    Usually, we have this 'if() goto cleanup;' pattern in our new
    code. It is going to be useful here too. Thing is, there was a
    memleak. If there has been an error in
    virNetServerProgramSendStreamError() or
    virNetServerProgramSendStreamData() created message was never
    freed.
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>