Add test for the mtu plugin

Change-Id: I94813ab6b06f227fdf91704e618908b492a604ef
Removes incorrect deprecation comments

Change-Id: I30525b92727d96c88701dc1f6a2dce2b6f46e8c8
Fixed userdata plugin return value for Python3

The comparison fails when ret_value is None in Python3.
This adds an extra check so that None will not be compared with an
integer.

Change-Id: Iddc6bbf42fc3215248d9187725a329181f2ba2fb
Merge "Add test for the mtu plugin"