Adjust import order according to PEP8 imports rule

This patch just adjust import order to follow PEP8 imports rule.
See http://www.python.org/dev/peps/pep-0008/#imports
Imports should be grouped in the following order:

    standard library imports
    related third party imports
    local application/library specific imports

Change-Id: I6d92e9eda72d83cbf940b7699268f884bd4045c1
Merge "Adjust import order according to PEP8 imports rule"