regex for plugin settings clarified
regex for plugin settings clarified

Change-Id: I2661a90961a7501287ac439d5193ab078597a1a1
Closes-Bug: #1594356
Closes-Bug: #1594360
Closes-Bug: #1594365

stackforge/fuel-plugin-contrail,stackforge/fuel-plugin-contrail,stackforge/fuel-plugin-contrail,stackforge/fuel-plugin-contrail