RFR: 8302226 failure_handler native.core should wait for coredump to finish on linux

[Ludvig Janiuk]

Update open/test/failure_handler/src/share/conf/linux.properties to handle core dumps more correctly.

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Commit messages:
 - 8302226 failure_handler native.core should wait for coredump to finish on linux

Changes: https://git.openjdk.org/jdk/pull/12515/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12515&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302226
  Stats: 5 lines in 1 file changed: 3 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/12515.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12515/head:pull/12515

PR: https://git.openjdk.org/jdk/pull/12515