[SPARK-19450] Replace askWithRetry with askSync.

## What changes were proposed in this pull request?

`askSync` is already added in `RpcEndpointRef` (see SPARK-19347 and https://github.com/apache/spark/pull/16690#issuecomment-276850068) and `askWithRetry` is marked as deprecated.
As mentioned SPARK-18113(https://github.com/apache/spark/pull/16503#event-927953218):

>askWithRetry is basically an unneeded API, and a leftover from the akka days that doesn't make sense anymore. It's prone to cause deadlocks (exactly because it's blocking), it imposes restrictions on the caller (e.g. idempotency) and other things that people generally don't pay that much attention to when using it.

Since `askWithRetry` is just used inside spark and not in user logic. It might make sense to replace all of them with `askSync`.

## How was this patch tested?
This PR doesn't change code logic, existing unit test can cover.

Author: jinxing <jinxing@meituan.com>

Closes #16790 from jinxing64/SPARK-19450.