RFR: 8338550: Do libubsan1 installation in test container only on Ubuntu

[Matthias Baesken]

After [JDK-8333144](https://bugs.openjdk.org/browse/JDK-8333144) docker related tests do not work on manually configured distros other than the 'standard' Ubuntu. This is because the basic generated Dockerfile with the change from [JDK-8333144](https://bugs.openjdk.org/browse/JDK-8333144) assumes 'apt-get' being available, which is not the case when one runs the testing on RPM based distributions.
So let's limit the libubsan1 installation to Ubuntu;  also add an 'apt-get update' to get recent package lists.

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Commit messages:
 - JDK-8338550

Changes: https://git.openjdk.org/jdk/pull/20624/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20624&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338550
  Stats: 5 lines in 1 file changed: 1 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/20624.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20624/head:pull/20624

PR: https://git.openjdk.org/jdk/pull/20624