Fix openssl s_client invocation

Signed-off-by: Max Fillinger <maximilian.fillinger@foxcrypto.com>
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 698c53a..0d13964 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -1985,7 +1985,7 @@
 
     run_test    "$TLS_VERSION_PRINT: Export keying material (OpenSSL compatibility)" \
                 "$P_SRV debug_level=4 force_version=$TLS_VERSION exp_label=test-label" \
-                "$O_CLI -keymatexport=test-label" \
+                "$O_CLI -keymatexport test-label" \
                 0 \
                 -s "Exporting key of length 20 with label \".*\": 0x" \
                 -c "Keying material exporter:" \