net-mgmt/check_nwc_health: Update to 7.8. From the ChangeLog:

• GLPLugin with better ip4/ip6 handling
• fix huawei subclasses
• interfaces --name filter expression can contain _adminup_ as a secondary filter
• route modes can handle v6
• use OSPFV3-MIB, support v6
• add CISCO-BGP4-MIB, support v6

Reported by: portscout
Approved by: matthew (mentor, implicit)