Snapshot ApfFilter before apply the new RA filters

Take a snapshot of ApfFilter before the new RA filter change at commit
hash: 75b432a6. Renamed it to LegacyApfFilter. The LegacyApfFilter will
be used to create a kill-switch of the new RA filter change.

Test: TH
Change-Id: I1d2254025d6e035ba86cd152d0b791bd946b3a5f
1 file changed