This commit changes the plugin interface so that we have update() functions
that can upate any attributes of the port or network. In the future when we
add more things like operational state this will give us the flexibility to be
able to update those. This also allows data extensions to be passed into the
update calls.
Thanks to Tyler and the others at cisco for making the changes to the cisco
plugins and tests (their patch is included in this commit).
Change-Id: If8a0111a7174d94d9f0aed9630e326d428ef994a