Fix H302 violations in extensions package

H302 violation is reported by flake8 when importing separated objects from
modules instead of importing the whole module.
e.g.   from package.module import function
       function()
is changed to
       from package import module
       module.function()

Change-Id: I570eeee2a7633c1590b54ac98b411a71fc9d4f4e
Partial-Bug: #1291032
Merge "Fix H302 violations in extensions package"