discovery_client: When a python measurement starts discovery service, hide discovery service logs

[vigkre]

• This contribution adheres to CONTRIBUTING.md.

What does this Pull Request accomplish?

• This PR redirects the logs to /dev/null (hide logs) when a python measurement starts discovery service.
• Before:

• After:

• Handle FileNotFoundError when wrong discovery service .exe path is specified for subprocess.popen function.
• Add tests to register service function to handle FileNotFoundError exception.

Why should this Pull Request be merged?

• Implements Task 2462367: When a python measurement starts discovery service, it should not show logs from discovery service to the user.

What testing has been done?

• Verified discovery service logs are not displayed.
• While the discovery service logs are hidden, it might hide other errors that might arise while starting discovery service through python measurement. To test this case:
  - Specified wrong discovery service .exe path to subprocess.popen function and noticed the log error is captured in the console:

[github-actions]

Test Results

     12 files  ±0       12 suites  ±0   18m 17s ⏱️ + 1m 2s
   180 tests ±0     180 ✔️ ±0  0 💤 ±0  0 ❌ ±0 
2 148 runs  ±0  2 148 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 5f97556. ± Comparison against base commit dbbee49.

This pull request removes 1 and adds 1 tests. Note that renamed tests count towards both.

tests.unit.test_discovery_client ‑ test___discovery_service_unavailable___register_service_registration_failure

tests.unit.test_discovery_client ‑ test___discovery_service_exe_unavailable___register_service___registration_failure

♻️ This comment has been updated with latest results.