RFR: 8265690: Use the latest Ubuntu base image version in Docker testing [v2]

[Aleksey Shipilev]

On Thu, 22 Apr 2021 12:37:43 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Use latest Ubuntu base image to get latest glibc, so that host-built JDK has a higher chance to pass. Current "oraclelinux:7.6" image apparently has glibc 2.27. Please see the bug for more discussion.
>> 
>> Additional testing:
>>  - [x] `hotspot_containers` tests on Ubuntu 20.04 (glibc 2.31) -- used to fail, now passes
>>  - [x] `hotspot_containers` tests on Debian 9 (glibc 2.24) -- continues to pass
>>  - [x] `hotspot_containers` tests on Centos 7 (glibc 2.17) -- continues to pass
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains one additional commit since the last revision:
> 
>   8265690: Use latest Ubuntu base image version in Docker testing

Well, I think `latest` is fine here, and it matches what other arches are doing in the same test. This also helps us not to update the test every time new development environments appear. Stable CIs should probably just set the test properties for the environments that CI servers run. That would also be the way out for those who may potentially run in incompatibilities. I've checked that the more or less wide spectrum of environments is fine. 

OK for me to push this?

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PR: https://git.openjdk.java.net/jdk/pull/3605