add a dummy SSLContext#security_level= implementation

Author: kares

src/main/java/org/jruby/ext/openssl/SSLContext.java

@@ -613,6 +613,12 @@ public RubyHash session_cache_stats(final ThreadContext context) {
         return RubyHash.newHash(context.runtime);
     }
 
+    @JRubyMethod(name = "security_level=")
+    public IRubyObject set_security_level(ThreadContext context, IRubyObject level) {
+        warn(context, "WARNING: SSLContext#security_level= has no effect under JRuby");
+        return context.nil;
+    }
+
     boolean isProtocolForServer() {
         return protocolForServer;
     }