hooks: add net-firewall/ebtables to the /var exception

BUG=b:150613151
TEST=emerge-mistral ebtables now succeeds

Change-Id: I9b6711c448e25def584b61fb577a39bec99593f4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/2081837
Tested-by: Aileen Cheng <chengaileen@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
diff --git a/hooks/filesystem-sanity.py b/hooks/filesystem-sanity.py
index ce666d4..94d6e70 100755
--- a/hooks/filesystem-sanity.py
+++ b/hooks/filesystem-sanity.py
@@ -107,6 +107,7 @@
     'media-sound/alsa-utils',
     'net-analyzer/netperf',
     'net-dns/dnsmasq',
+    'net-firewall/ebtables',
     'net-firewall/iptables',
     'net-fs/samba',
     'net-misc/chrony',