tests/netgraph: Tests for ng_bridge

[donner]

Summary

Test functionality of ng_bridge(4):

• replicating traffic to anything but the sending hook
• persistence
• detect loops
• unicast to only one link of many
• stretch to implementation limits on broadcast
• uplink in private/classic vlan mode

Depends on D30629

Test Plan

# kyua test bridge
bridge:basic  ->  passed  [0.435s]
bridge:loop  ->  passed  [0.113s]
bridge:many_broadcasts  ->  expected_failure: netgraph queue full (191): 1 checks failed as expected; see output for more details  [12.604s]
bridge:many_unicasts  ->  expected_failure: response too large: 1 checks failed as expected; see output for more details  [54.589s]
bridge:persistence  ->  passed  [0.006s]
bridge:uplink_classic  ->  passed  [0.600s]
bridge:uplink_private  ->  passed  [0.601s]

[donner]

• Remove cleanup functions. Does not work as expected.

[donner]

• Test learned unicast

[donner]

• Differentiate the tests by receiving hook expectations

[donner]

• Add tests for uplink in private vlan mode

[donner]

• Test for uplink in classic mode

[donner]

• Add msg_handler in order to receive messages to util.
• Add tests for the amount of learned mac addresses.

[donner]

• Either expect known problems not related to ng_brigde or pass if they are fixed.

[donner]

• Rebased to D30657

Depends on D30657

[donner]

• Style source