Declare the bandwidth thresholds in % : Switch from 80, 90 to 80%, 90%
This permit a better comprehension when defining the thresholds.
This also aligned the error, discard and bandwidth thresholds declarations.

When interface is admin UP and oper DOWN, the 2 displayed elements into the short output are in red.

In some cases, the interface Alias will contains a "|" as a field separator.
This character will break the check and split the output at the wrong place.

Replace the "|" character with a "!”

The check finish in panic when the index file isn't accessible, in this case in "permission denied"

Error of the os.Stat function not correctly handle in the file.AsExp() function

When the uptime is lower than the last pollingn the elements are forced to 0.
But on some interfaces, these elements aren't available and the old data are at nul.
When the check try to force the old datas to 0, it failed into panic because of nil pointer

On vlanxxx interfaces, the value returned by the devices are incorrect.
To avoid wrong triggered alerts, force the bandwidth usage to 0 when interfaces are called vlanxxx

the HTML table have some issues :

• the cellpadding isn't applied
• Bordercolor isn't well applied
• OK, Warning and Critical cell have to be tuned for better visualization

When the interface name contains one or several '/' the JSON file can't be created and the check fail in unknown mode with the error, file xxx.json can't be created.
With this character, the path become wrong : /var/tmp/check_snmp_interface_foreach/127.0.0.1_SNMPv2c/Ethernet1/1.json

Fix it by replacing the '/' by an '_'