bugfix: Should keep retrying singleEventFeed

[suzaku]

What problem does this PR solve?

partialRegionFeed should keep retrying singleEventFeed until the region is no longer valid.
So the maxRetries parameter should be set to 0.

What is changed and how it works?

Set maxRetries to be 0.

Check List

Tests

• Unit test

[amyangfei]

I prefer to use a finite retry time. If some API in partialRegionFeed always returns error and context is not canceled by other routines, the loop will not exits then.

[suzaku]

@july2993 What do you think? In your original implementation maxRetries was not set.

[july2993]

keep use a finite retry time?

[suzaku]

OK