Revert "Use wrappers instead of direct calls to ip route."

This commit somehow broken floating ips with the l3 agent so we should revert
it till we figure out why.

This reverts commit f80f06a71de6e235c71e0333448cf59e44745c45.

Change-Id: Ic93eec0d95ad20baf53cc97476fcdff1b308ae91