junos parser for 'show ddos-protection' command

[karlnewell]

This is a junos parser for
show ddos-protection protocols [optional_protocol] statistics brief | display xml

The parser creates a separate measurement for each protocol group, protocol type, and KPI combination and pulls stats for received packets, dropped packets, packet rate, and violation count.

I recommend you include a statement for each protocol you want to collect data for in your commands.yaml file. You can omit the optional_protocol and the command will pull stats for all protocols which will likely result in 800+ separate measurements.

Example data set:

> show ddos-protection protocols sample statistics brief
Packet types: 7, Received traffic: 0, Currently violated: 0

Protocol    Packet      Received        Dropped        Rate     Violation State
group       type        (packets)       (packets)      (pps)    counts
sample      aggregate   0               0              0        0         ok
sample      syslog      0               0              0        0         ok
sample      host        0               0              0        0         ok
sample      pfe         0               0              0        0         ok
sample      tap         0               0              0        0         ok
sample      sflow       0               0              0        0         ok

[karlnewell]

If there aren't any issues, can you please merge this PR?