Avoid throwing exception on decrypt failure

[Copilot]

The decryption logic was throwing OSError exceptions when openssl cms or openssl smime commands failed, causing the handler to crash instead of gracefully handling decryption failures.

Changes

• Wrapped waagent.RunSendStdin() calls in try-except blocks to catch OSError exceptions
• Added fallback logic: attempts openssl cms first (FIPS 140-3 compliant), then falls back to openssl smime if the first fails
• Added logging to track which decryption method succeeded or failed

for decrypt_cmd in [cms_cmd, smime_cmd]:
    try:
        output = waagent.RunSendStdin(decrypt_cmd, unencodedSettings)
        if output[0] == 0 and output[1]:
            protected_settings_str = output[1]
            break
        else:
            self.log('Attempt to decrypt protectedSettings with "{0}" failed (rc={1}).'.format(decrypt_cmd, output[0]))
    except OSError:
        pass

The handler now continues execution even if both decryption methods fail, allowing the extension to handle missing protected settings appropriately rather than crashing.

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