Documentation for fireOnOneCallback parameter of DeferredList is incorrect

[exarkun]

The __init__ docstring says this about fireOnOneCallback:

When this flag is set, the DeferredList will fire with a two-tuple: the first element is the index in C{deferredList} of the Deferred which fired; the second element is the result of that Deferred.

The implementation of the flag looks like this, though:

            if succeeded == SUCCESS and self.fireOnOneCallback:
                self.callback((result, index))

[exarkun]

(In [30757]) Branching to 'fireononecallback-4882'

[exarkun]

(In [30758]) Swap the order of the index and result in the documentation

refs #4882

[ralphm]

Awesome! Please merge.

[exarkun]

(In [30762]) Merge fireononecallback-4882

Author: exarkun Reviewer: ralphm Fixes: #4882

Correct the API documentation for the fireOnOneCallback parameter of DeferredList.