Fixing error message typo (#643)
Fixing error message typo (#643)

Addresses point 2 in
https://github.com/istio/istio.github.io/issues/91
kyessenov/pilot,kyessenov/pilot,kyessenov/pilot,kyessenov/pilot,istio/old_pilot_repo,istio/old_pilot_repo,istio/old_pilot_repo,vadimeisenbergibm/pilot,vadimeisenbergibm/pilot,vadimeisenbergibm/pilot