update file node test to cope with occasional failure
update file node test to cope with occasional failure

HiroyasuNishiyama/node-red,namgk/node-red,mw75/node-red,mw75/node-red,btsimonh/node-red,node-red/node-red,HiroyasuNishiyama/node-red,namgk/node-red,HiroyasuNishiyama/node-red,node-red/node-red,mw75/node-red,btsimonh/node-red,btsimonh/node-red,node-red/node-red,mw75/node-red