Update clusterdefinition.md (#2171)
Update clusterdefinition.md (#2171)

Fix apiserver options table markdown
yangl900/acs-engine,yangl900/acs-engine,rjtsdl/acs-engine,jackfrancis/acs-engine,Azure/acs-engine,jackfrancis/acs-engine,Azure/acs-engine,yangl900/acs-engine,rjtsdl/acs-engine,yangl900/acs-engine,yangl900/acs-engine,jackfrancis/acs-engine,Azure/acs-engine,rjtsdl/acs-engine,Azure/acs-engine,jackfrancis/acs-engine,rjtsdl/acs-engine,jackfrancis/acs-engine,Azure/acs-engine,rjtsdl/acs-engine