Fix 'panic: shorthand redefinition' for istioctl mixer subcommand (#651)
Fix 'panic: shorthand redefinition' for istioctl mixer subcommand (#651)

Immediate fix is to remove mixer `-m` short flag option to avoid
conflict with the manager API server address. Slightly longer term fix
is to fetch manager/mixer API server address from a config map instead
of depending on environment variables or flags.
mandarjog/istio,mandarjog/istio,smawson/istio,sebastienvas/istio,istio/istio,sebastienvas/istio,mandarjog/istio,geeknoid/istio,istio/istio,istio/istio,istio/istio,frankbu/istio,frankbu/istio,frankbu/istio,mandarjog/istio,geeknoid/istio,mandarjog/istio,frankbu/istio,smawson/istio,istio/istio,smawson/istio,smawson/istio,smawson/istio,sebastienvas/istio,geeknoid/istio,sebastienvas/istio,geeknoid/istio,geeknoid/istio,frankbu/istio,frankbu/istio,sebastienvas/istio,geeknoid/istio,smawson/istio