ebs br: avoid infinite loop to check tikv gc and schedule pause status

[BornChanger]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. Run EBS snapshot BR
2. Shutdown one TiKV node

2. What did you expect to see? (Required)

EBS BR backup job should fail with timeout in less than 10 mins

3. What did you see instead (Required)

EBS BR backup job job falls into infinite loop

4. What is your TiDB version? (Required)

TiDB 6.5 & TiDB 7.1 & nightly

[BornChanger]

/label component/br

[ti-chi-bot]

@BornChanger: The label(s) component/br cannot be applied. These labels are supported: fuzz/sqlancer, challenge-program, compatibility-breaker, first-time-contributor, contribution, require-LGT3, good first issue, correctness, duplicate, proposal, security, needs-more-info, needs-cherry-pick-release-5.2, needs-cherry-pick-release-5.3, needs-cherry-pick-release-5.4, needs-cherry-pick-release-6.0, needs-cherry-pick-release-6.1, needs-cherry-pick-release-6.2, needs-cherry-pick-release-6.3, needs-cherry-pick-release-6.4, needs-cherry-pick-release-6.5, needs-cherry-pick-release-6.6, needs-cherry-pick-release-7.0, needs-cherry-pick-release-7.1, needs-cherry-pick-release-7.2, needs-cherry-pick-release-7.3, affects-5.2, affects-5.3, affects-5.4, affects-6.0, affects-6.1, affects-6.2, affects-6.3, affects-6.4, affects-6.5, affects-6.6, affects-7.0, affects-7.1, affects-7.2, affects-7.3, may-affects-5.2, may-affects-5.3, may-affects-5.4, may-affects-6.0, may-affects-6.1, may-affects-6.2, may-affects-6.3, may-affects-6.4, may-affects-6.5, may-affects-6.6, may-affects-7.0, may-affects-7.1, may-affects-7.2, may-affects-7.3.

In response to this:

/label component/br

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[BornChanger]

/label affects-6.5 affects-7.1