Refactor configuring of floating ips on a router

This approach to configuring floating ips is stateless and idempotent.
This allows it to handle corner cases, such as reusing a floating ip
address with a different floating ip id in a way that is easier to
understand.

The concept is to wipe the floating ips clean and rebuild them each
time with the following optimizations.  To avoid bad performance in
manipulating iptables, it is called in the context of a call to
defer_apply_on.  To avoid a disruption in network flow a set
difference is use to determine the set of addresses that no longer
belong on the inteface rather than removing them all blindly.

Change-Id: I98aacbbb52b35688036990961d02e0b273504a77
Fixes: Bug #1209011
Lower severity of log trace for DB integrity error

LOG.exception is not appropriate, since a concurrent
port creation can occur and it has been dealt with
in the except block.

This avoids spooking users who are on the hunt for
real bugs.

Supports fix for 1239637

Change-Id: I9489702ee63db0b004fe41195fa4727af261d514
Imported Translations from Transifex

Change-Id: I38683ac890169536497e2c1ed9178d00a441328b
Merge "Refactor configuring of floating ips on a router"
Merge "Imported Translations from Transifex"
Merge "Lower severity of log trace for DB integrity error"