[jdk17u] RFR: 8273894: ConcurrentModificationException raised every time ReferralsCache drops referral

[Aleksey Shipilev]

On Fri, 1 Oct 2021 09:17:28 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Clean backport to fix the ReferralsCache bug.
> 
> Additional testing: 
>  - [x] Linux x86_64 fastdebug `jdk_security`

Got the push approval.

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PR: https://git.openjdk.java.net/jdk17u/pull/128