unlink METADATA_VERSION_FILE_NAME before rewrite it, fix no such key thrown

[CheSema]

In private repo I see that the race is possible between attaching parts and removing condemned parts.
Removing process reads files, those files are supposed to be immutable. But attach process changes content in METADATA_VERSION_FILE_NAME file in a way that hard linked file in condemned directory also is changed.

https://d1k2gkhrlfqv31.cloudfront.net/clickhouse-test-reports-private/json.html?REF=master&sha=a71ec07a0761d5e1a8eb4bf2ec3d6e40d20708fc&name_0=MasterCI&name_1=Stateless%20tests%20%28amd_msan%2C%20meta%20storage%20in%20keeper%2C%20s3%20storage%2C%20parallel%2C%202%2F2%29&name_1=Stateless%20tests%20%28amd_msan%2C%20meta%20storage%20in%20keeper%2C%20s3%20storage%2C%20parallel%2C%202%2F2%29

This change is not related to public but the function is shared between repos and this code would work correctly for both.

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[clickhouse-gh]

Workflow [PR], commit [4825f59]

Summary: ❌

job_name	test_name	status	info	comment
Integration tests (arm_binary, distributed plan, 3/4)		failure
	test_keeper_memory_soft_limit/test.py::test_soft_limit_create	FAIL
Integration tests (arm_binary, distributed plan, 4/4)		failure
	test_trace_log_memory_context/test.py::test_memory_context_in_trace_log	FAIL