add error stack for resolve-lock test

[youjiali1995]

Signed-off-by: youjiali1995 zlwgx1023@gmail.com

1. Add the error stack to distinguish the failure cause easily.
2. Don't keep running the test if PD is down.

[youjiali1995]

I changed the way to handle PD's EOF error accoriding to @vivid392845427 words. Now if the test gets the EOF error, it will backoff for a while and if backoff times out, the test finishes with sucess to avoid false-negative caused by the test environment. @zyguan @vivid392845427

[vivid392845427]

LGTM