Issue description

register a new instance to Eureka,but can't proxy to this instance

Environment

• apisix version (cmd: apisix version): 1.4
• OS:mac os

Minimal test code / Steps to reproduce the issue

What's the actual result? (including assertion message & call stack if applicable)

oldnode host":"172.16.50.93","port":8888
newnode host":"172.16.50.93","port":8081
apisix balance proxy to oldnode not to newnode
after make reload it‘s OK

What's the expected result?