Use JUnit TemporaryFolder rule instead of system temp folder

[yuppie-flu]

This should help to avoid transient failures, mentioned in #6013 (comment) when running tests in parallel. Otherwise several tests use the same /tmp working folder.

[gianm]

LGTM after CI 👍

[gianm]

Hi @yuppie-flu, there seems to be some problem with the new forbidden-api check:

[ERROR] Failed to execute goal de.thetaphi:forbiddenapis:2.3:check (validate) on project java-util: Parsing signatures failed: Class 'org.apache.commons.io.FileUtils' not found on classpath while parsing signature: org.apache.commons.io.FileUtils#getTempDirectory() -> [Help 1]

[yuppie-flu]

Thank you @gianm
I had to remove this check, cause there are some modules, which do not depend on apache commons-io. forbiddenapis maven plugin is configured only once in parent pom.xml.
If we really need to forbid this, the simplest solution would be overriding failOnMissingClasses property I guess.

[leventov]

@yuppie-flu failOnUnresolvableSignatures. Please set it to true and include FileUtils in the forbidden-apis config, it's fine.

Also in the future, don't force push into the PR branch, only add commits on top. See https://github.com/apache/incubator-druid/blob/master/CONTRIBUTING.md

[yuppie-flu]

@leventov Done, thank you