Signed-off-by: Donatas Abraitis <[email protected]>

Example:
```
 # HELP iptables_default_packets_total iptables_exporter: Total packets matching a chain's default policy.
 # TYPE iptables_default_packets_total counter
 iptables_default_packets_total{chain="DOCKER",command="iptables-save",policy="-",table="filter"} 0
 iptables_default_packets_total{chain="DOCKER",command="iptables-save",policy="-",table="nat"} 0
0iptables_default_packets_total{chain="DOCKER-ISOLATION-STAGE-1",command="iptables-save",policy="-",table="filter"} 0
 iptables_default_packets_total{chain="DOCKER-ISOLATION-STAGE-2",command="iptables-save",policy="-",table="filter"} 0
-iptables_default_packets_total{chain="DOCKER-USER",command="iptables-save",policy="-",table="filter"} 0
-iptables_default_packets_total{chain="FORWARD",command="ip6tables-save",policy="ACCEPT",table="filter"} 0
:iptables_default_packets_total{chain="FORWARD",command="iptables-save",policy="DROP",table="filter"} 0
-iptables_default_packets_total{chain="INPUT",command="ip6tables-save",policy="ACCEPT",table="filter"} 633
-iptables_default_packets_total{chain="INPUT",command="iptables-save",policy="ACCEPT",table="filter"} 4.4871354e+07
:iptables_default_packets_total{chain="INPUT",command="iptables-save",policy="ACCEPT",table="nat"} 26812
-iptables_default_packets_total{chain="OUTPUT",command="ip6tables-save",policy="ACCEPT",table="filter"} 606
-iptables_default_packets_total{chain="OUTPUT",command="iptables-save",policy="ACCEPT",table="filter"} 2.7409757e+07
 iptables_default_packets_total{chain="OUTPUT",command="iptables-save",policy="ACCEPT",table="nat"} 118690
```

Signed-off-by: Donatas Abraitis <[email protected]>

Just for readability.

Signed-off-by: Donatas Abraitis <[email protected]>