xentrace: close output file in the function which opened it

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: George Dunlap <george.dunlap@cloud.com>

tools/xentrace/xentrace.c

@@ -794,7 +794,6 @@ static void monitor_tbufs(void)
     free(meta);
     free(data);
     /* don't need to munmap - cleanup is automatic */
-    close(outfd);
 }
 
 
@@ -1225,6 +1224,7 @@ int main(int argc, char **argv)
 
     monitor_tbufs();
 
+    close(outfd);
     return 0;
 }