non_atomic_requests decorator alters _non_atomic_requests attribute of original function

[Alasdair Nicol]

When calling non_atomic_requests with a function, it alters the _non_atomic_requests attribute of the original function.

Here's an example:

from django.db import transaction

@transaction.non_atomic_requests(using='default')
def my_view(request):
    return HttpResponse('')

assert my_view._non_atomic_requests == {'default'}  # passes

wrapped_view = transaction.non_atomic_requests(using='other')

assert wrapped_view._non_atomic_requests == {'default', 'other'}  # passes
assert my_view._non_atomic_requests == {'default'}  # fails

I realise that this is a contrived example. It isn't an issue when non_atomic_requests is used as a decorator:

@transaction.non_atomic_requests(using='default')
@transaction.non_atomic_requests(using='other')
def my_view(request)
    return HttpResponse('')