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The behaviour of the firewallReplaceUidChain was incorrect in
several ways:

1. It was missing the "always allow TCP RST packets" rules which
   were added in http://ag/963000 .
2. It included a RETURN statement at the end of blacklist chains,
   which is superfluous since all user-defined chains implicitly
   return, and became incorrect when http://ag/963000 switched the
   behaviour of blacklist chains from inserting new rules at the
   beginning to appending them at the end.
3. It was missing the rules to allow the types of ICMPv6 packets
   that are critical in maintaining connectivity.

By itself, this change is a no-op since nothing currently calls
firewallReplaceUidRule.

Bug: 26675191
Change-Id: I985e6861812908cbe7eaf0f54ca0ad39c22bbfeb