fix snprintf length argument

Author: wkliao

darshan-runtime/lib/darshan-core.c

@@ -497,7 +497,7 @@ void darshan_core_shutdown(int write_log)
         err = close(mmap_fd);
         if (err < 0)
             darshan_core_fprintf(stderr, "darshan:log duplication close (%s)\n", strerror(errno));
-        snprintf(dup_log_fame, strlen(final_core->mmap_log_name), "%s.dup",
+        snprintf(dup_log_fame, strlen(final_core->mmap_log_name)+5, "%s.dup",
                  final_core->mmap_log_name);
         dup_mmap_fd = open(dup_log_fame, O_CREAT | O_WRONLY, 0644);
         if (dup_mmap_fd != -1) {