Allow non-NIST-P256 TLS server keys

[sethterashima]

Description

Fixes a regression in a safety check on the TLS key that prevented the HTTP proxy server from launching.

The intended purpose of the safety check is to verify that the user is not using the same key as both a TLS server key and a command-authentication key. The code tries to load the TLS key as a command-authentication key, and then compares it with the actual command-authentication key. If the loading step fails because the TLS key is not a NIST-P256 key, then everything is fine. There's no way it could be being misued. However, a loading failure was being treated as a fatal error.

Fixes #359

Type of change

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• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Bug fix (non-breaking change which fixes an issue)
• Documentation update

Checklist:

Confirm you have completed the following steps:

• My code follows the style of this project.
• I have performed a self-review of my code.
• I have made corresponding updates to the documentation.
• I have added/updated unit tests to cover my changes.