Add 0.18.0 to .backportrc.json to facilitate backport.

[abhishekrb19]

@suneet-s, I found the backport.md doc useful when trying to backport this fix to 0.18.0. Adding 0.18.0 to the config, so we could just run backport from the repo's working directory. Thanks!

[suneet-s]

LGTM Thanks @abhishekrb19 !

[abhishekrb19]

One of the tests failed, but appears to be unrelated to this change:

[INFO] Running org.apache.druid.server.initialization.JettyTest
[ERROR] Tests run: 14, Failures: 0, Errors: 8, Skipped: 2, Time elapsed: 52.23 s <<< FAILURE! - in org.apache.druid.server.initialization.JettyTest
[ERROR] testNumConnectionsMetricHttps(org.apache.druid.server.initialization.JettyTest)  Time elapsed: 5.878 s  <<< ERROR!
java.lang.RuntimeException: Connections greater than 0
	at org.apache.druid.server.initialization.JettyTest.waitForJettyServerModuleActiveConnectionsZero(JettyTest.java:520)
	at org.apache.druid.server.initialization.JettyTest.testNumConnectionsMetricHttps(JettyTest.java:496)

However, the test ran fine locally on my mac:

[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running org.apache.druid.server.initialization.JettyTest
[WARNING] Tests run: 8, Failures: 0, Errors: 0, Skipped: 2, Time elapsed: 10.404 s - in org.apache.druid.server.initialization.JettyTest
[INFO]
[INFO] Results:
[INFO]
[WARNING] Tests run: 8, Failures: 0, Errors: 0, Skipped: 2
[INFO]
[INFO]
[INFO] --- animal-sniffer-maven-plugin:1.17:check (check-java-api) @ druid-server ---
[INFO] Checking unresolved references to org.codehaus.mojo.signature:java18:1.0
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  33.406 s
[INFO] Finished at: 2020-04-09T21:40:13-07:00
[INFO] ------------------------------------------------------------------------

@suneet-s, is this a known issue? I force pushed to re-trigger another job to see what happens.

[suneet-s]

#9633 tried to fix this and should have been merged 2 days ago - any chance your branch did not have this change?

Usually if it's a flaky test, one of the committers can re-trigger just the failed test on travis so you don't need to do a force push and re-run all the tests.

[abhishekrb19]

@suneet-s, the commit 7bf2dfa seems to exist in the branch:

❯ git branch --contains 7bf2dfa
  fix_markdown_numbered_list
* include_0.18.0_to_backport
  master

Ah, thanks, good to know about selectively re-triggering failed tests on Travis.

[jihoonson]

LGTM