Code under test cannot write to file passed as parameter

[tyuldashev]

Description
Test file prepared by UTBot is not writable for client code.

To Reproduce
Steps to reproduce the behavior:

1. Generate tests for char file_fwrite(FILE*, int) function from c-examples
2. Run generated tests

Expected behavior
Content of test file A is update according to code logic, i.e. Posititve, Negative or Zero written to file.

Actual behavior
Content of the file is not modified and consists of 64 \0