DOCS: Added note about Fuel bug
DOCS: Added note about Fuel bug

  While verification it was discovered that user
  can be confused by error when trying to remove
  Ceph OSD node from cluster. This change just
  added NOTE to user guide.

Change-Id: I3dab3744ca4f57234d461c3acf9a4a7b641bde95

stackforge/fuel-plugin-cinder-netapp