Need to install runit to make 'chpst' work.

Many jobs are started by using 'chpst' in ctl files. I think we need to add it as part of the stemcell instead of report executing failed in nise_bosh. 

BTW, I also added monit part in my local env to make processes strong and do monitoring. We can also use 'monit start  job_name' to make jobs run. But I don't know if this part is needed in nise_bosh?