Set tls_session.server_key too

It doesn't seem to be used, but mimic the tls automation implementation.
https://github.com/secdev/scapy/blob/5160430bd16c6084d5aef2a10e47dc0455aace40/scapy/layers/tls/automaton_srv.py#L243-L245

converters/tls.py

@@ -4,6 +4,7 @@
     TLSApplicationData,
     Cert,
     PrivKey,
+    PrivKeyRSA,
     tlsSession,
     load_nss_keys,
 )
@@ -35,7 +36,9 @@ def handle_stream(self, stream: Stream) -> Result:
         tls_session.ipdst = stream.Metadata.ServerHost
         if key_path.exists():
             key = PrivKey(key_path)
-            tls_session.server_rsa_key = key
+            tls_session.server_key = key
+            if isinstance(key, PrivKeyRSA):
+                tls_session.server_rsa_key = key
         if cert_path.exists():
             cert = Cert(cert_path)
             tls_session.server_certs = [cert]