Fix issue #1577 so junos logical interface link status and mtu are captured

[mjbear]

Fix juniper_junos_show_interfaces template for issue #1577 and other minor enhancements

• correct five digit dotted decimal to be a correct IPv4 dotted quad
• capture logical interface link state on the "Flags:" line (topic of juniper_junos_show_interfaces incorrect parsing of state for irb interfaces #1577)
• capture logical interface inet Protocol MTU

Notes:

• logical interfaces have no data for admin_state so it is an empty string
• logical interfaces have no data for hardware_type so it is an empty string

[andyb2000]

Tested on my environment here and confirm this is working as expected. Parsed output:

{'admin_state': '',
  'description': 'Customer: interface:',
  'destination': 'x.x.x.x/29',
  'hardware_type': '',
  'interface': 'irb.6027',
  'link_status': 'Up',
  'local': 'x.x.x.y',
  'mtu': '1514'},

[mjbear]

Tested on my environment here and confirm this is working as expected. Parsed output:

{'admin_state': '',
  'description': 'Customer: interface:',
  'destination': 'x.x.x.x/29',
  'hardware_type': '',
  'interface': 'irb.6027',
  'link_status': 'Up',
  'local': 'x.x.x.y',
  'mtu': '1514'},

@jvanderaa
There's additional confirmation beyond unit tests that this fix works. Thank you for reviewing and merging this in!