RFR: CODETOOLS-7903147: unrooted relative paths in checkI18NProps.sh

[Jonathan Gibbons]

Please review a reasonably small fix to improve the test that checks localization resources.

Previously, the code created temporary files in the source directory for the script itself.  The script is changed to accept a new leading parameter which is a directory in which to store temporary files.

In addition, the names of the temporary files are made longer and less cryptic.

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Commit messages:
 - fix whitespace
 - CODETOOLS-7903147: unrooted relative paths in checkI18NProps.sh

Changes: https://git.openjdk.java.net/jtreg/pull/68/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jtreg&pr=68&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903147
  Stats: 21 lines in 3 files changed: 5 ins; 2 del; 14 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/68.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/68/head:pull/68

PR: https://git.openjdk.java.net/jtreg/pull/68