Bugzilla importer should not ask for project key and project lead for existing JIRA projects

Bugzilla importer allows the user to enter a project key for the Bugzilla project (being imported) with the same name as already existing project in JIRA. As a result no such project is created (JIRA ensures the uniqness of project names) and Bugzilla issues are imported into the existing JIRA project.

This is confusing as the project does not get created and the only message about that is in the import logs, e.g.

Project: TestProduct already exists. Not imported
0 projects imported from Bugzilla.

The steps to reproduce this:

1. import TestProduct from the attached Bugzilla MySQL dump, give it project key TESTA
2. notice that project TESTA (key) - TestProduct (name) was created and it has one issue TESTA-1
3. use the same import steps, but this time around give it the project key TESTB
4. notice that project TESTB was NOT created and issue was imported into TESTA as TESTA-2

The fix for this would be to recognize that issues for a project will be imported to the existing JIRA project with the same project name and instead of input fields for project key and project lead, only text displaying the existing JIRA project key and lead should presented to the user (read-only).