Fix dynamic security configuration possibly not being reloaded on Windows only.

Closes #1962. Thanks to martgeier.

ChangeLog.txt

@@ -3,6 +3,8 @@ Broker:
   messages. Closes #1968.
 - mosquitto_connect_bind_async() and mosquitto_connect_bind_v5() should not
   reset the bind address option if called with bind_address == NULL.
+- Fix dynamic security configuration possibly not being reloaded on Windows
+  only. Closes #1962.
 
 Build:
 - Fix man pages not being built when using CMake. Closes #1969.

plugins/dynamic-security/plugin.c

@@ -346,8 +346,8 @@ static int dynsec__config_load(void)
 	char *json_str;
 	cJSON *tree;
 
-	/* Save to file */
-	fptr = fopen(config_file, "rt");
+	/* Load from file */
+	fptr = fopen(config_file, "rb");
 	if(fptr == NULL){
 		return 1;
 	}