Fix config fetcher-related error logging

[adams85]

Describe the purpose of your pull request

Fixes error logging in HttpConfigFetcher.FetchInternalAsync to include exception in the log if any (to make the behavior consistent with other SDKs.)

Requirement checklist (only if applicable)

• [x] I have covered the applied changes with automated tests.
• [x] I have executed the full automated test set against my changes.
• [x] I have validated my changes against all supported platform versions.
• [x] I have read and accepted the contribution agreement.

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

100.0% Coverage
0.0% Duplication