Clarify IntelliJ IDEA Jar Hell fix

[catalin-ursachi]

Clarified the instructions for fixing IntelliJ's idea_rt.jar Jar hell issue (as updated by #27614); specifically, that:

• Setting Shorten command line to classpath file is only necessary if the launcher is disabled via a JVM option.
• If the launcher is disabled via an idea.properties setting, a restart is required (even though IntelliJ doesn't prompt you for one).

[elasticmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[rjernst]

I think the instructions adding the setting to idea.properties should stay next to the clause about 2017.2, and the 2017.3 instructions should be it's own sentence(s) after that.

[catalin-ursachi]

So:

In order to run tests directly from IDEA 2017.2 and above, it is required to disable the IDEA run launcher in order to avoid idea_rt.jar causing "jar hell". This can be achieved by adding the -Didea.no.launcher=true JVM option, or by adding idea.no.launcher=true to the idea.properties file which can be accessed under Help > Edit Custom Properties (this will require a restart of IDEA). For IDEA 2017.3 and above, in addition to the JVM option, you will need to go to Run->Edit Configurations... and change the value for the Shorten command line setting from user-local default: none to classpath file.

?

[rjernst]

Yes, but I would separate the "or" portion about idea.properties into a separate sentence (it sounds like a run-on sentence right now). Perhaps begin with Alternatively, `idea.no.launcher=true` can be set in the `idea.properties` file...

[rjernst]

Thanks @catalin-ursachi, looks good now.