Clarify key types message from ssl_client2 and ssl_server2

If no key is loaded in a slot, say "none", not "invalid PK".

When listing two key types, use punctuation that's visibly a sequence
separator (",").

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 691c0e7..4d2679b 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -1556,7 +1556,7 @@
             0 \
             -c "Verifying peer X.509 certificate... ok" \
             -c "Ciphersuite is TLS-ECDHE-ECDSA" \
-            -s "key types: Opaque - invalid PK" \
+            -s "key types: Opaque, none" \
             -s "Ciphersuite is TLS-ECDHE-ECDSA" \
             -S "error" \
             -C "error"
@@ -1575,7 +1575,7 @@
             -c "key type: Opaque" \
             -c "Verifying peer X.509 certificate... ok" \
             -c "Ciphersuite is TLS-ECDHE-ECDSA" \
-            -s "key types: Opaque - invalid PK" \
+            -s "key types: Opaque, none" \
             -s "Verifying peer X.509 certificate... ok" \
             -s "Ciphersuite is TLS-ECDHE-ECDSA" \
             -S "error" \