Handle PAN-OS poller cleaning edge cases

[GigleGig]

Test inclusion requirements

No new tests were added; this change hardens existing PAN-OS cleaners without altering expected behaviour. Verified with:
CONDA_NO_PLUGINS=true conda run -n suzieq pytest tests/unit/poller/worker/services/test_service.py

Related Issue

Fixes #992

Description

PAN-OS devices occasionally emit ARP/ND rows without a state and MTU data that isn’t valid JSON. The poller crashed while cleaning those responses. This patch normalises missing states and parses MTU blobs defensively so malformed payloads raise warnings instead of exceptions.

Type of change

• Bug fix (non-breaking change which fixes an issue)

New Behavior

• PAN-OS ARP/ND cleaner defaults absent states to an empty string before mapping to permanent, reachable, or failed.
• PAN-OS interface cleaner validates MTU payload strings; malformed blobs are skipped with a warning.

Contrast to Current Behavior

• Previously, missing state values caused AttributeError and malformed MTU blobs caused JSONDecodeError, aborting the poller.

Discussion: Benefits and Drawbacks

• Benefits: improves poller resilience for PAN-OS without impacting other platforms; backwards-compatible.
• Drawbacks: none identified.

Changes to the Documentation

• None required.

Proposed Release Note Entry

• Fix PAN-OS poller crashes triggered by missing ARP state values and malformed interface MTU data.

Comments

• Tests executed: CONDA_NO_PLUGINS=true conda run -n suzieq pytest tests/unit/poller/worker/services/test_service.py

Double Check

• I have read the comments and followed the CONTRIBUTING.md.
• I have explained my PR according to the information in the comments or in a linked issue.
• My PR source branch is created from the develop branch.
• My PR targets the develop branch.
• All my commits have --signoff applied