Resolve "Crash in self_test.py related to suffix variable"

• Related issues: #934 (closed)
• Requested reviewers: @tamarapu

Reason why this change is needed

The scripts ./self_test.py crashes due to unknown variable named suffix

Description of the change

Initialized suffix to empty string

Affected operating points

All BE. Change affects only self_test.py script.

Related to #934 (closed)