RFR: JDK-8261518: jpackage looks for main module in current dir when there is no module-path [v5]

[Andy Herrick]

> when the app modules have already been jlinked with the runtime, and there is no need for module-path, jpackage was acting as if the module-path was "." and picking up jars in the current directory.

Andy Herrick has updated the pull request incrementally with one additional commit since the last revision:

  JDK-8261518: jpackage looks for main module in current dir when there is no module-path

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2781/files
  - new: https://git.openjdk.java.net/jdk/pull/2781/files/fa5b3622..afd59c25

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2781&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2781&range=03-04

  Stats: 40 lines in 2 files changed: 12 ins; 16 del; 12 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2781.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2781/head:pull/2781

PR: https://git.openjdk.java.net/jdk/pull/2781