RFR: 8238781: [macos] jpackage tests failed due to "hdiutil: convert failed" in various ways

[Alexander Matveev]

This is similar issue we used to have for hdiutil create/detach, but for "convert". Added same workaround to repeat command. I also added repeat for "udifrez" command just in case.

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

Commit messages:
 - 8238781: [macos] jpackage tests failed due to "hdiutil: convert failed" in various ways

Changes: https://git.openjdk.java.net/jdk/pull/1687/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1687&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8238781
  Stats: 8 lines in 1 file changed: 6 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1687.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1687/head:pull/1687

PR: https://git.openjdk.java.net/jdk/pull/1687