RFR: 8276994: java/nio/channels/Channels/TransferTo.java leaves multi-GB files in /tmp [v2]

[Markus KARG]

> This PR proposes to cleanup *all* temp files of the `TransferTo` test, not just the 2GB files. Also it separates the actual test logic from the cleanup logic, so the test cases are simple to understand again as they are not interwoven with cleanup code anymore.

Markus KARG has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:

 - Revert "Cleaning up temp files"
   
   This reverts commit 1fead836777782791943d08b5feae06fa49035dd.
 - Cleaning up temp files
   
   Signed-off-by: Markus Karg <markus at headcrashing.eu>

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

Changes: https://git.openjdk.java.net/jdk/pull/6379/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6379&range=01
  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6379.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6379/head:pull/6379

PR: https://git.openjdk.java.net/jdk/pull/6379