store: does not validate --block-sync-concurrency parameter

[aymericDD]

Thanos, Prometheus and Golang version used:

thanos, version 0.23.1 (branch: HEAD, revision: 5327cd8b9bd56ce4912fe602197ad04ab2722b18)
  build user:       root@0acc901868e9
  build date:       20211005-12:08:29
  go version:       go1.16.8
  platform:         linux/amd64

Object Storage Provider: S3

What happened:

If the value of --block-sync-concurrency parameter is not greater than 1 the program is blocked. In my case I have set this parameter to 0.5 value and no error was displayed.

What you expected to happen:

The program must failed with an error message like :
error: the block sync concurrency must be positive

How to reproduce it (as minimally and precisely as possible):

thanos store --objstore.config-file=config.yml--block-sync-concurrency=0.5

Full logs to relevant components:

Logs

level=info ts=2021-10-06T12:35:06.138837351Z caller=factory.go:46 msg="loading bucket configuration"
level=info ts=2021-10-06T12:35:06.139832953Z caller=inmemory.go:172 msg="created in-memory index cache" maxItemSizeBytes=131072000 maxSizeBytes=1073741824 maxItems=maxInt
level=info ts=2021-10-06T12:35:06.140665189Z caller=options.go:27 protocol=gRPC msg="enabling server side TLS"
level=info ts=2021-10-06T12:35:06.141404778Z caller=options.go:57 protocol=gRPC msg="server TLS client verification enabled"
level=info ts=2021-10-06T12:35:06.144707145Z caller=store.go:424 msg="starting store node"
level=info ts=2021-10-06T12:35:06.144987518Z caller=intrumentation.go:60 msg="changing probe status" status=healthy
level=info ts=2021-10-06T12:35:06.145025188Z caller=http.go:62 service=http/server component=store msg="listening for requests and metrics" address=0.0.0.0:10902
level=info ts=2021-10-06T12:35:06.14528623Z caller=store.go:359 msg="initializing bucket store"
level=info ts=2021-10-06T12:35:07.966819426Z caller=fetcher.go:476 component=block.BaseFetcher msg="successfully synchronized block metadata" duration=1.821507188s cached=90 returned=90 partial=0

Anything else we need to know:

[GiedriusS]

Fixed in #4753