Fix SyncOnCommit always return false in API of push_mirrors (#23088) (#23100)
Backport #23088
Fix: #22990
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Before, the return value of the api is always false,regrardless of
whether the entry of `sync_on_commit` is true or false.
I have confirmed that the value of `sync_on_commit` dropped into the
database is correct.
So, I think it is enough to make some small changes.