tests: Increase test coverage of jirahook submodule

This is just a commit to increase the coverage of the test case for jirahook webhook.

There are several pieces of the code that are not being tested. Some simple checks in existing tests can solve that, but others require separated test cases.

This is not part of #589 sub tasks but it could be.

Signed-off-by: Julio Faracco jfaracco@redhat.com