[GOBBLIN-2162] Only load added jars in the cache

[Will-Lo]

Dear Gobblin maintainers,

Please accept this PR. I understand that it will not be reviewed until I have checked off all the steps below!

JIRA

• My PR addresses the following Gobblin JIRA issues and references them in the PR title. For example, "[GOBBLIN-XXX] My Gobblin PR"
  • https://issues.apache.org/jira/browse/GOBBLIN-2162

Description

• Here are some details about my PR, including screenshots (if applicable):

When Gobblin launches a YARN app, if the cache is enabled it will load all the jars stored in the cache into the classpath.

This can be problematic as jars that persisted from older versions of jars or other executions may clobber the classpath, adding jars that are not needed or jars that interfere with the current jars.

This PR ensures that only the jars that were intended to be uploaded by the GobblinYarnAppLauncher are the only jars that are loaded into the classpath from the shared cache.

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference JIRA issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

[phet]

just needs a test!

[phet]

don't we have a getPath or a getString that takes a default?

let's call within a getAppLibJarList(this.config) utility, which would offer far more facile testability