Check and create binlogdir and avrodir before use

The binlog and avro file directories should be checked before they are
used and if they don't exist, they should be created.

server/modules/routing/avrorouter/avro.c

@@ -497,7 +497,7 @@ createInstance(SERVICE *service, char **options)
         MXS_ERROR("No 'binlogdir' option found in source service, in parameters or in router_options.");
         err = true;
     }
-    else
+    else if (ensure_dir_ok(inst->binlogdir, R_OK) && ensure_dir_ok(inst->avrodir, W_OK))
     {
         snprintf(inst->binlog_name, sizeof(inst->binlog_name), BINLOG_NAMEFMT, inst->fileroot, first_file);
         inst->prevbinlog[0] = '\0';