querierd v0.4

Changes

• Support for adding/removing interfaces at runtime, with new test
• Add querierctl tool, with plain text API over UNIX domain socket
  • Shows elected querier per VLAN, querierctl show
  • Shows elected querier timeout
  • Shows which port the elected querier is connected to on bridge
  • Support for displaying bridge mdb show in human-friendly format

Fixes

• Fix rearming of internal timers, caused wrong querier timeout
  handling and querierd jumping in too early
• Never allow link-local addresses to win a querier election
• Never allow 0.0.0.0 address to win a querier election