[tools] delete_candidate failing

[CamilleBeau]

Describe the bug
The delete_candidate.php script is failing because it is using test_name as tableName. The script must instantiate an instrument and get tableName instead.

To Reproduce
Steps to reproduce the behavior (attach screenshots if applicable):

1. Run delete_candidate for a candidate that has an instrument with a different table name / test name
2. See error

[driusan]

fixed by merged PR