Add nullptr check in logCertVerificationFailure

[thisisnsh]

Problem statement

• In logCertVerificationFailure following pointers were not null checked before accessing them:
  • X509_STORE_CTX cert context
  • X509 cert
  • X509_NAME subject name

Proposed changes

• In logCertVerificationFailure check pointers are not null before accessing them
• Add tests
• Add error code, message and depth to log for better debugging

Remaining work

• Unit Tests
• Integration Tests
• Documentation