Improve handling of serial numbers and asset tags

[Razmuzh]

2020-02-07 08:48:05,796 [DEBUG] Received HTTP Status 400.
2020-02-07 08:48:05,797 [WARNING] NetBox failed to create devices object. A duplicate record may exist or the data sent is not acceptable.
2020-02-07 08:48:05,797 [DEBUG] NetBox 400 status reason: {"serial":["This field may not be null."]}
2020-02-07 08:48:05,798 [DEBUG] Unaccepted request data: {'name': 'esxvmware205', 'device_type': {'model': 'PowerEdge R810'}, 'device_role': {'name': 'Server'}, 'platform': {'name': 'VMware ESXi'}, 'site': {'name': 'vCenter'}, 'serial': None, 'asset_tag': None, 'cluster': {'name': 'CL01-GF-DEV'}, 'status': 'active', 'tags': ['Synced', 'vCenter', 'p-114-288-001']}

[Razmuzh]

Got around it by editing line 443 in run.py to:
serial_number = "00000000"

[synackray]

Thanks for the report @Razmuzh! I will apply a permanent fix to this for the upcoming release.

[synackray]

Corrected with the use of netbox object templates. Non-required fields with None values will not be passed to NetBox to avoid this in the future.