This will ensure that mtu is set whenever setup_hm_port()
is called regardless of if the port has just been created
or not. Also checks mtu in update-status hook.
Change-Id: I80b5cea812becd1724fcfe2a8a232253eac76735
Closes-Bug: #2018998
(cherry picked from commit f326ef267a)
(cherry picked from commit 3ebb523f89)
(cherry picked from commit 1fa839826f)
(cherry picked from commit 5747bcad93)
(cherry picked from commit 31cb8fe1eb)