The original change had to be reverted because it caused
tests failing in the gate. The failures were due to the
fact that when a port was not ready, an exception was
thrown to trigger a full resync of the agent. This
behavior was meant to be temporary and was fixed in a
dependent patch that was not merged though. This revert
moves the handling of not ready ports in this patch.
It also refactors the unit tests a bit.
This reverts commit e7270d9505.
Change-Id: I6574cef3c95525ace6a98cf968ee159190681394
ccdf211b4c