Add blocked per client counter

[DL6ER]

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This adds a new counter for blocked queries per client. This duplicates the functionality we already have for domains (either total or blocked count).

The new info can be queried from the API by specifying the keyword blocked in addition to >top-clients. This option is in agreement with other available options, e.g. >top-clients withzero blocked (29) will work as expected.

This template was created based on the work of udemy-dl.

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/top-blocked-domains-per-client/5055/6

[PromoFaux]

This appears to be working as written.

I had an odd moment where pihole-FTL got stuck, and I could not stop or restart it (with either service or systemctl), though that may be unrelated. Once I rebooted the pi I could control it again. I may have had a rogue process...

pi@pihole:~ $ sudo service pihole-FTL stop
pi@pihole:~ $ sudo service pihole-FTL status
● pihole-FTL.service - LSB: pihole-FTL daemon
   Loaded: loaded (/etc/init.d/pihole-FTL; generated; vendor preset: enabled)
   Active: inactive (dead) since Thu 2018-05-10 22:30:16 UTC; 44s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 4120 ExecStop=/etc/init.d/pihole-FTL stop (code=exited, status=0/SUCCESS)
  Process: 3701 ExecStart=/etc/init.d/pihole-FTL start (code=exited, status=0/SUCCESS)

May 10 22:28:21 pihole systemd[1]: Starting LSB: pihole-FTL daemon...
May 10 22:28:21 pihole pihole-FTL[3701]: Not running
May 10 22:28:21 pihole su[3724]: Successful su for pihole by root
May 10 22:28:21 pihole su[3724]: + ??? root:pihole
May 10 22:28:21 pihole su[3724]: pam_unix(su:session): session opened for user pihole by (uid=0)
May 10 22:28:21 pihole pihole-FTL[3701]: dnsmasq: failed to bind DHCP server socket: Address already in use
May 10 22:28:21 pihole systemd[1]: Started LSB: pihole-FTL daemon.
May 10 22:30:16 pihole systemd[1]: Stopping LSB: pihole-FTL daemon...
May 10 22:30:16 pihole pihole-FTL[4120]: Not running
May 10 22:30:16 pihole systemd[1]: Stopped LSB: pihole-FTL daemon.
pi@pihole:~ $ sudo netstat -tulpn
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:53              0.0.0.0:*               LISTEN      3960/pihole-FTL

[PromoFaux]

Discussed issue above internally with @DL6ER, he cannot see how it would be related to this branch