Fix the bug that created the node at ecs driver
Fix the bug that created the node at ecs driver

1, From the official document can know parameter param['IoOptimized'] type is string and his value is ``none`` or ``optimized``

andrewsomething/libcloud,techhat/libcloud,Kami/libcloud,andrewsomething/libcloud,watermelo/libcloud,SecurityCompass/libcloud,vongazman/libcloud,apache/libcloud,pquentin/libcloud,mistio/libcloud,t-tran/libcloud,Scalr/libcloud,apache/libcloud,StackPointCloud/libcloud,ByteInternet/libcloud,andrewsomething/libcloud,StackPointCloud/libcloud,techhat/libcloud,SecurityCompass/libcloud,ZuluPro/libcloud,techhat/libcloud,pquentin/libcloud,illfelder/libcloud,samuelchong/libcloud,ByteInternet/libcloud,Scalr/libcloud,ZuluPro/libcloud,samuelchong/libcloud,mgogoulos/libcloud,erjohnso/libcloud,samuelchong/libcloud,mistio/libcloud,watermelo/libcloud,watermelo/libcloud,erjohnso/libcloud,ZuluPro/libcloud,ByteInternet/libcloud,vongazman/libcloud,illfelder/libcloud,t-tran/libcloud,mgogoulos/libcloud,Scalr/libcloud,illfelder/libcloud,Kami/libcloud,t-tran/libcloud,Kami/libcloud,vongazman/libcloud,mistio/libcloud,erjohnso/libcloud,SecurityCompass/libcloud,StackPointCloud/libcloud,apache/libcloud,mgogoulos/libcloud,pquentin/libcloud