get_lldp_neighbors fails when ChassisId is truncated

[Robin Gilijamse]

When neighbor devices have a very long Chassis ID, looking up this value in the MIB fails:

File "/home/rgilijamse/scripts/_venv/lib/python3.8/site-packages/napalm_procurve/procurve.py", line 423, in _lldp_detail_parser
    "{}.0.{}.1".format(key_mib_table[key], ifs[interface])
KeyError: 'ChassisId'

Easy to fix: add the correct MIB id to key_mib_table in _lldp_detail_parser (line 388)

"ChassisId": "lldpRemChassisId",

[Robin Gilijamse]

I can add a PR for this if you want, but it'll take me some time to set up an environment for that.