RFR: 8318580 : "javax/swing/MultiMonitor/MultimonVImage.java failing with Error. Can't find library: /open/test/jdk/java/awt/regtesthelpers" after JDK-8316053

[lawrence.andrews]

1) Fixed the @library regtesthelpers file path 
2) Added @build PassFailJFrame
3) Added a empty line at the end of the file that was missing.

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Commit messages:
 - 8318580 : "javax/swing/MultiMonitor/MultimonVImage.java failing with Error. Can't find library: /open/test/jdk/java/awt/regtesthelpers" after JDK-8316053

Changes: https://git.openjdk.org/jdk/pull/16408/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16408&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318580
  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/16408.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16408/head:pull/16408

PR: https://git.openjdk.org/jdk/pull/16408