DescribeOpenAPIEndpoint需要支持securityToken

[cheyang]

目前setEndpointByLocation中DescribeOpenAPIEndpoint仅支持AK，不支持token。先开个issue记录，随后会修复。

DescribeOpenAPIEndpoint error: Aliyun API Error: RequestId: 884535BB-75EA-4C90-A7CB-304709835FD5 Status Code: 
400 Code: MissingSecurityToken Message: SecurityToken is mandatory for this action. 
with  client 
&{AccessKeyId:STS.xxxxxx    AccessKeySecret:xxxxxx  && 
securityToken: debug:false 
httpClient:0xc42034e360 endpoint:https://location.aliyun        
cs.com version:2015-06-12 serviceCode: regionID: 
businessInfo: 
userAgent:

[menglingwei]

@cheyang 我确认了一下，目前location不支持sts