check mesh before configuring mixerSAN (#2918)
check mesh before configuring mixerSAN (#2918)

Signed-off-by: Guihua Zhu <e83bbfd87aadbe7cfb451ba15697e0ec8cec64e7@gmail.com>
frankbu/istio,frankbu/istio,geeknoid/istio,smawson/istio,geeknoid/istio,geeknoid/istio,geeknoid/istio,frankbu/istio,istio/istio,istio/istio,istio/istio,frankbu/istio,geeknoid/istio,smawson/istio,smawson/istio,smawson/istio,istio/istio,smawson/istio,smawson/istio,geeknoid/istio,frankbu/istio,frankbu/istio,istio/istio