ANDROID: xt_quota2: clear quota2_log message before sending

Initialize message buffer for quota2_log to avoid sending
random data.

Bug: 196046570
Test: passed netd test suites
Fixes: 10cda83af99d ("ANDROID: netfilter: xt_quota2: adding the
original quota2 from xtables-addons")
Signed-off-by: Todd Kjos <tkjos@google.com>
Change-Id: Ic9f34aaa2593809b375fc649b74567190c99dc62

Author: toddkjos

net/netfilter/xt_quota2.c

@@ -106,23 +106,16 @@ static void quota2_log(unsigned int hooknum,
 		return;
 	}
 	pm = nlmsg_data(nlh);
+	memset(pm, 0, sizeof(*pm));
 	if (skb->tstamp.tv64 == 0)
 		__net_timestamp((struct sk_buff *)skb);
-	pm->data_len = 0;
 	pm->hook = hooknum;
 	if (prefix != NULL)
 		strlcpy(pm->prefix, prefix, sizeof(pm->prefix));
-	else
-		*(pm->prefix) = '\0';
 	if (in)
 		strlcpy(pm->indev_name, in->name, sizeof(pm->indev_name));
-	else
-		pm->indev_name[0] = '\0';
-
 	if (out)
 		strlcpy(pm->outdev_name, out->name, sizeof(pm->outdev_name));
-	else
-		pm->outdev_name[0] = '\0';
 
 	NETLINK_CB(log_skb).dst_group = 1;
 	pr_debug("throwing 1 packets to netlink group 1\n");