RFR: 7903017: RunTestsHandler passes arguments to lastIndexOf in the wrong order

[Liam Miller-Cushon]

This fixes a bug where the arguments to to `lastIndexOf` were swapped.

The first argument to `String#lastIndexOf(int, int)` is a character to search for, the second argument is a start index.

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

Commit messages:
 - 7903017: RunTestsHandler passes arguments to lastIndexOf in the wrong order

Changes: https://git.openjdk.java.net/jtharness/pull/12/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jtharness&pr=12&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903017
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jtharness/pull/12.diff
  Fetch: git fetch https://git.openjdk.java.net/jtharness pull/12/head:pull/12

PR: https://git.openjdk.java.net/jtharness/pull/12