Fix missing "tmp_path" in tiflash configuration make cluster_manager can not start (#4106)

[ti-chi-bot]

This is an automated cherry-pick of #4106

What problem does this PR solve?

Issue Number: close #4091

Problem Summary:

Without "tmp_path" in the config.toml, the cluster_manager.py fail to start itself without any error message in the logging files

[root@main-cluster-tiflash-2 root]# /tiflash/flash_cluster_manager/flash_cluster_manager --config /data0/config.toml
Traceback (most recent call last):
  File "flash_cluster_manager.py", line 8, in <module>
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "PyInstaller/loader/pyimod03_importers.py", line 531, in exec_module
  File "conf.py", line 23, in <module>
  File "flash_tools.py", line 17, in __init__
KeyError: 'tmp_path'

https://github.com/pingcap/tics/blob/release-5.4/cluster_manage/flash_tools.py#L17

What is changed and how it works?

Only get "tmp_path" when we actually need it, and give it a default value if not exist

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• CalvinNeo
• JaySon-Huang

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[CalvinNeo]

LGTM

[JaySon-Huang]

/merge

[ti-chi-bot]

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 7799107

[sre-bot]

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