FreeBSD CI: perform memory leak test as well as Linux/Windows

and also move `vpncmd /tools /cmd:check` under .ci directory.

.ci/vpntools-check.sh

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+set -eux
+
+./build/vpncmd /tools /cmd:check

.cirrus.yml

@@ -10,7 +10,8 @@ FreeBSD_task:
     - ./configure
     - make -j $(sysctl -n hw.ncpu || echo 4) -C tmp
     - ldd build/vpnserver
-    - build/vpncmd /tool /cmd:check
+    - .ci/memory-leak-test.sh
+    - .ci/vpntools-check.sh
 
 FreeBSD_task:
   freebsd_instance:
@@ -25,4 +26,5 @@ FreeBSD_task:
     - ./configure
     - make -j $(sysctl -n hw.ncpu || echo 4) -C tmp
     - ldd build/vpnserver
-    - build/vpncmd /tool /cmd:check
+    - .ci/memory-leak-test.sh
+    - .ci/vpntools-check.sh