net-mgmt/py-napalm: Update to 3.0.0

• Remove the patch that fixed some issues with net-mgmt/py-junos-eznc as it has been merged by upstream.
  
  Get rid of the post-patch target as well because it's no longer required.

Changelog with some notable changes/fixes:

General:

• Integrated nxapi_plumbing and pyIOSXR into NAPALM.
• Updated support for TwoGigabit & TwentyFiveGig interfaces to canonical_map.py

NXOS:

• Fix exception when trying to get environmental data from certain Nexus devices

IOS:

• Fix traceroute output parsing in ios
• Fix vrf detection when no vrf is defined
• Fix show interfaces summary for 10/40/100 Gig Interfaces
• Fix get_bgp_neighbors_detail

IOS-XE:

• Update to handle Cisco ISR mac address table with multiple EHWIC modules installed

IOS-XR:

• Add support for XML namespace prefixes in find_txt

Junos:

• Added auto_probe optional argument
• Add support for configure private in Junos
• SRX cluster devices stack RPC replies under multi-routing-engine-results

https://github.com/napalm-automation/napalm/releases/tag/3.0.0

MFH: 2020Q2