Upgrade to 2.6 breaks document counts due to driver change

[donstephan]

Going through the necessary upgrade for 2.6 and this one jumped out to me. This happens in the exposure functionality around document counts. There's a discussion going on about it:

meteor/meteor#11921

Shouldn't be too tricky to fix but need to trick the enforeMaxLimit to not get set with cursors that are going to be used for counts.