When solving SKARA-1385, I found the following issue:

If the PR has an approved CSR and then someone types `/csr unneeded`, the bot currently replies `determined that a CSR request is not needed for this pull request.` But it is wrong, the bot should reply `The CSR requirement cannot be removed as there is already a CSR associated with the main issue...`.

It is because the following code which judges whether the PR has `csr` label, doesn't distinguish these two situations: 1. the CSR has been approved, 2. no csr request before.

```
// file CSRCommand.java
        if (cmd.equals("unneeded") || cmd.equals("uneeded")) {
            // ignore some code
            if (!labels.contains(CSR_LABEL)) {
                // FIXME here, the PR may have an approved CSR. We should distinguishing the situations
                // about having no csr request and (having csr request && the CSR has been approved).
                reply.println("determined that a [CSR](https://wiki.openjdk.java.net/display/csr/Main) request " +
                        "is not needed for this pull request.");
                return;
            }
            // ignore some code
        }
```