nailgun-agent: use service command to restart mcollective
nailgun-agent: use service command to restart mcollective

mcollectived can be launched via upstart job or systemd unit.
Fortunately the service command hides those gory details.

Change-Id: Iad4c8bc5d89176513b4d3bcc37a4161a9d900caf
Related-Bug: #1454741

prmtl/fuel-web,huntxu/fuel-web,huntxu/fuel-web,huntxu/fuel-web,eayunstack/fuel-web,prmtl/fuel-web,SmartInfrastructures/fuel-web-dev,SmartInfrastructures/fuel-web-dev,prmtl/fuel-web,stackforge/fuel-web,prmtl/fuel-web,nebril/fuel-web,nebril/fuel-web,eayunstack/fuel-web,stackforge/fuel-web,eayunstack/fuel-web,SmartInfrastructures/fuel-web-dev,SmartInfrastructures/fuel-web-dev,nebril/fuel-web,huntxu/fuel-web,eayunstack/fuel-web,prmtl/fuel-web,eayunstack/fuel-web,nebril/fuel-web,nebril/fuel-web,stackforge/fuel-web,huntxu/fuel-web,SmartInfrastructures/fuel-web-dev