Once HA port is set, it must remain this value no matter
what the server return. Because there is race condition
between l3-agent side sync router info for processing
and server side router deleting.
This patch adds a helper function for every ha_port set
action. If the ha_port is not None, it will always stay
with original value.
Closes-Bug: #1826726
Change-Id: I96a088d25048be02a9c5b12c1d087df075b36fc4
45957f12c8