RFR: 8263041: Shenandoah: Cleanup C1 keep alive barrier check [v3]

[Roman Kennke]

On Mon, 8 Mar 2021 15:32:25 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

>> Please review this cleanup. It appears that JDK-8233339 missed C1 change.
>> 
>> Test:
>> - [x] hotspot_gc_shenandoah
>
> Zhengyu Gu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Removed unrelated change

Looks good!

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Marked as reviewed by rkennke (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/2834