Host address and port values are not preserved in item test form after page reload for discovered items

Values of fields "Host address" and "Port" are not populated in the Item test form if item configuration page was reloaded (if for example "Execute now" or "Clear history and trends" were executed).
This problem occurs only for discovered items.

Steps to reproduce:

1. Open any host that has discovered items
2. Open configuration form of a discovered item
3. Press "Test" button and notice that fields "Host address" and "Port" are populated
4. Close item test form and press "Execute now" or "Clear history and trends" button
5. Press "Test" button again

Result:
In the opened Test item form fields "Host address" and "Port" are not populated.

Expected:
These fields should preserve their value when opening Test item form after page refresh, like it works for regular items and for templated items.

Example: