Fix H302 violations in unit tests

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: Ic6975f39c755ded54149a9c01fcdcfaf78c596fc
Partial-Bug: #1291032
Merge "Fix H302 violations in unit tests"