FIB - add/update/delete - MAC entries - add 100, del 10, add new 100, del 150

HLD:
test_l2_fib.py
config1
add 4 pg-l2 interfaces
configure them into l2bd
L2 MAC learning disabled in l2bd
program 100 MAC entries in L2 fib - 25 MACs per interface
test1
send L2 MAC frames between all 4 pg-l2 interfaces
verify1
all packets received correctly

config2
delete 12 MAC entries, 3 per interface
test2a
send L2 MAC frames between all 4 pg-l2 interfaces for non-deleted MAC entries
verify2a
all packets received correctly
test2b
try send L2 MAC frames between all 4 pg-l2 interfaces for deleted MAC entries
verify2b
no packet received on all 4 pg-l2 interfaces

config3
program new 100 MAC entries - 25 MACs per interface
test3
send L2 MAC frames between all 4 pg-l2 interfaces for all of 188 MAC entries in the FIB
verify3
all packets received correctly

config4
delete 160 MAC entries (40 MACs per interface)
test4a
send L2 MAC frames between all 4 pg-l2 interfaces for non-deleted MAC entries
verify4a
all packets received correctly
test4b
try send L2 MAC frames between all 4 pg-l2 interfaces for deleted MAC entries
verify4b
no packet received on all 4 pg-l2 interfaces