RFR: 1434: Testissue#addLink doesn't generate the right relationship for the reversed link

[Guoxiong Li]

Hi all,

This patch fixes the reversed link type. For example, when adding a `csr for` link at `ISSUE-1` which links to `ISSUE-2`, the `ISSUE-2` should have a reversed link `csr of` instead of the same link type `csr for`.

The reversed relations are shown below:
- `backported by` and `backport of`
- `csr for` and `csr of`
- `blocks` and `is blocked by`
- `clones` and `is cloned by`

And the `duplicates` link type doesn't have the reversed linke type like `duplicated by` now. So we should use the link type `duplicates` instead of `duplicated by` in the test cases so that the tests can be closer to the actual situation.

Thanks for taking the time to review.

Best Regards,
-- Guoxiong

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Commit messages:
 - SKARA-1434

Changes: https://git.openjdk.java.net/skara/pull/1325/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1325&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-1434
  Stats: 13 lines in 3 files changed: 5 ins; 0 del; 8 mod
  Patch: https://git.openjdk.java.net/skara/pull/1325.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1325/head:pull/1325

PR: https://git.openjdk.java.net/skara/pull/1325