Fix PSK invocation: OpenSSL client

Only s_server has a -nocert option, s_client doesn't. Fixes OpenSSL client
test cases in PSK-only builds.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index b40e322..031a9ce 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -500,7 +500,8 @@
 
 adapt_cmd_for_psk () {
     case "$2" in
-        *openssl*) s='-psk abc123 -nocert';;
+        *openssl*s_server*) s='-psk abc123 -nocert';;
+        *openssl*) s='-psk abc123';;
         *gnutls-*) s='--pskkey=abc123';;
         *) s='psk=abc123';;
     esac