Comment 'node.ssl_dist_optfile' option by default

etc/emq.conf

@@ -246,7 +246,7 @@ node.proto_dist = inet_tcp
 ## Value: File
 ##
 ## vm.args: -ssl_dist_optfile <File>
-node.ssl_dist_optfile = {{ platform_etc_dir }}/ssl_dist.conf
+## node.ssl_dist_optfile = {{ platform_etc_dir }}/ssl_dist.conf
 
 ## Sets the net_kernel tick time. TickTime is specified in seconds.
 ## Notice that all communicating nodes are to have the same TickTime