Small corrections to list_interfaces(). Also make pyproject.toml usable.

code/iottb/utils/tcpdump_utils.py

@@ -20,7 +20,7 @@ def list_interfaces() -> str:
     ensure_installed()
     try:
         result = subprocess.run(['tcpdump', '--list-interfaces'], capture_output=True, text=True, check=True)
-        return result.stdout
+        print(result.stdout)
     except subprocess.CalledProcessError as e:
         print(f'Failed to list interfaces: {e}')
         return ''