[bug] PHP classes completion to the backend_model attribute and tag not in the right files

[vasilii-b]

Preconditions (*)

1. Plugin with the latest version from 1.0.0-develop
2. Magento 2 Project in PHPStorm

Steps to reproduce (*)

1. Open any system.xml or config.xml file within a module
2. Edit or create a filed that is using the backend_model attribute
3. Change the PHP class name and see the suggestions based on the typed string
4. Save the currently opened file into the same directory with a different file name
5. Open the newly created file and perform the same action as on step Reference for file path declared in XMl/JavaScript are broken #3.

Expected result (*)

The PHP class completion for backend_model does not happen in other files than system.xml and config.php.

Actual result (*)

The PHP class completion for backend_model happen in other files than system.xml and config.php.

Related Links
Issue #89 Completion. Add PHP classes completion to the backend_model attribute and tag
MR #89 : Completion. Add PHP classes completion to the backend_model attribute and tag