Allow IPv6 formats to use colons without port

[xmacan]

The problem is when the hostname of the device is in the format aaaa:bbbb:...This conflicts with cacti_snmp_get/walk functions due to the additional the port number
cacti_escapeshellarg($hostname) . ':' . $port . ' ' .

actual 1.2x branch

[TheWitness]

This issue was resolved here: #5875