fix of redhat init-scripts, closes #LOGSTASH-2040 and #LOGSTASH-2062

closes #LOGSTASH-2040
- stdout and stderror of the logstash process should be redirected to /dev/null, so automation tools can quit cleanly

closes #LOGSTASH-2062
- according to the Linux Standard Base Core Specification starting a running service should return 0
-see http://refspecs.linuxbase.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html