Revert "tls: allow wildcards in common name"

This reverts commit 45024e7b.

It's making test/simple/test-tls-check-server-identity.js fail:

  AssertionError: Test#4 failed: { host: 'b.a.com',
    cert: { subject: { CN: '*.a.com' } },
    result: false }
      at <omitted>/test/simple/test-tls-check-server-identity.js:201:10