Read the cert file as X509Certificate2 instead of the lowly

X509Certificate, because the former can read pkcs12 files
which is the only way we can load a certificate file which
contains a private key.

Else, using normal .pem cert files, without a key results in
an X509Certificate* with no private key, hence failing the
challege response part of the ssl handshake when required

Author: essiene

src/client/api/SslOption.cs

@@ -80,7 +80,7 @@ public bool Enabled
 
         private SslProtocols m_version = SslProtocols.Ssl3;
 
-        ///<summary>Retrieve or set the path to client certificate.
+        ///<summary>Retrieve or set the Ssl protocol version
         ///</summary>
         public SslProtocols Version
         {
@@ -107,7 +107,7 @@ public X509CertificateCollection Certs
                     return null;
                 } else {
                     X509CertificateCollection c = new X509CertificateCollection();
-                    c.Add(X509Certificate.CreateFromCertFile(m_certPath));
+                    c.Add(new X509Certificate2(m_certPath));
                     return c;
                 }
             }