Dell N1500.pm: LLDP detection doesn't work

[nqb]

Describe the bug
When you enabled VoIP detection using Dell N1500 switch module, LLDP detection returns a wrong MAC in @phones array. I got: 0x:48:7a:5e:1a:fa (wrong prefix and last two chars missing).

To Reproduce
Steps to reproduce the behavior:

1. Configure a Dell N1500 to do VoIP detection using LLDP
2. Plug a voice phone (not see by PacketFence previously)

=> Phone is not auto-registered.

Expected behavior
@phones array should contain a correct MAC and voice phone should be auto-registered.

Additional context
Regex to catch MAC seems to be a bit different than for other vendors.

I got this behavior on a 6.6.0.15 firmware with Dell N1500 switch.