SERVER-14662 changed positional projections and positional updates to error if multiple arrays were encountered when matching the filter. This change had undesirable effects. Users were no longer able to issue the following positional projections and positional updates:

> db.c.insert({a: [1, 2], b: [3, 4]})
> db.c.find({a: 1, b: 4}, {"a.$": 1})

> db.c.insert({a: [1, 2], b: [3, 4]})
> db.c.update({a: 1, b: 4}, {$set: {"a.$": 5}})

We will no longer error in these cases.