Fix leaks for keeper with rocksdb storage (iterators was not destroyed)

[azat]

Changelog category (leave one):

• Bug Fix (user-visible misbehavior in an official stable release)

Changelog entry (a user-readable short description of the changes that goes into CHANGELOG.md):

Fix leaks for keeper with rocksdb storage (iterators was not destroyed)

CI: https://s3.amazonaws.com/clickhouse-test-reports/PRs/84084/a27e4fcb365a35641c75fc886c90dafc8418b812//unit_tests_asan/job.log

[clickhouse-gh]

Workflow [PR], commit [028fe59]

Summary: ❌

job_name	test_name	status	info	comment
Stateless tests (amd_asan, distributed plan, sequential)		failure
	00002_log_and_exception_messages_formatting	FAIL
Stress test (amd_msan)		failure
	Server died	FAIL
	Hung check failed, possible deadlock found (see hung_check.log)	FAIL
	Killed by signal (in clickhouse-server.log)	FAIL
	Fatal message in clickhouse-server.log (see fatal_messages.txt)	FAIL
	Killed by signal (output files)	FAIL
	Found signal in gdb.log	FAIL
Performance Comparison (amd_release, master_head, 3/3)		error
Finish Workflow		failure
	python3 ./ci/jobs/scripts/workflow_hooks/new_tests_check.py	failure

[azat]

CI:

Stateless tests (amd_asan, distributed plan, sequential)

• 00002_log_and_exception_messages_formatting

Stress test (amd_msan)

• assertHasValidVersionMetadata - fix is in progress

Performance Comparison (amd_release, master_head, 3/3)

• some internal issues cc @maxknv