Fix decorator uses which crash newer pylint

Pylint version:

  pylint 0.25.1,
  astng 0.23.1, common 0.58.0

crashes when passing the fully-qualified decorator name with:

  File "/usr/lib/pymodules/python2.7/pylint/checkers/base.py", line 161, in visit_function
    if not redefined_by_decorator(node):
  File "/usr/lib/pymodules/python2.7/pylint/checkers/base.py", line 116, in redefined_by_decorator
    decorator.expr.name == node.name):
AttributeError: 'Getattr' object has no attribute 'name'

I found out that simply using a shortened name will 'fix' this issue,
so let's do this to allow running newer pylint versions.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>