Containerized network check reports the host metrics (#994)
Containerized network check reports the host metrics (#994)

* network: PEP8, 257 and obvious context manager
* network: force pid 1 in custom procfs, do not support ss and netstat if custom procfs is set

DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core