starting a already running service should return exit code 0

according to the Linux Standard Base Core Specification this shouldn't be 99 but 0
see http://refspecs.linuxbase.org/LSB_3.1.1/LSB-Core-generic/LSB-Core-generic/iniscrptact.html
fixes https://logstash.jira.com/browse/LOGSTASH-2040

stderror still open after calling /etc/init.d/logstash start
You should redirect stderror AND stdout of logstash to /dev/null, so all outputs are closed cleanly and automation tools reading the output of the init-script can quit cleanly.
Merge pull request #1213 from ImmobilienScout24/fix/init-scripts

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