RFR: 7902698: Collision of zero timestamp as a special value with use in filesystems [v3]

[Liam Miller-Cushon]

> This fixes a bug when the timestamp of a test file is set to zero, since jtharness currently uses zero as a special value. See discussion in [CODETOOLS-7902698](https://bugs.openjdk.java.net/browse/CODETOOLS-7902698).

Liam Miller-Cushon has updated the pull request incrementally with one additional commit since the last revision:

  Fix com.sun.javatest.SelectionTest failure

-------------

Changes:
  - all: https://git.openjdk.java.net/jtharness/pull/22/files
  - new: https://git.openjdk.java.net/jtharness/pull/22/files/c988435a..d6fef84d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jtharness&pr=22&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jtharness&pr=22&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jtharness/pull/22.diff
  Fetch: git fetch https://git.openjdk.java.net/jtharness pull/22/head:pull/22

PR: https://git.openjdk.java.net/jtharness/pull/22