CDRIVER-735 fix aggregate test
CDRIVER-735 fix aggregate test

A reused index variable meant not all of the test was ever run. Also,
remove some test code for MongoDB 2.0, now long obsolete, that might
have masked future regressions.

mschoenlaub/mongo-c-driver,acmorrow/mongo-c-driver,rcsanchez97/mongo-c-driver,jmikola/mongo-c-driver,ksuarz/mongo-c-driver,Machyne/mongo-c-driver,Machyne/mongo-c-driver,acmorrow/mongo-c-driver,ajdavis/mongo-c-driver,christopherjwang/mongo-c-driver,derickr/mongo-c-driver,mongodb/mongo-c-driver,malexzx/mongo-c-driver,beingmeta/mongo-c-driver,remicollet/mongo-c-driver,jmikola/mongo-c-driver,Machyne/mongo-c-driver,remicollet/mongo-c-driver,christopherjwang/mongo-c-driver,ksuarz/mongo-c-driver,derickr/mongo-c-driver,remicollet/mongo-c-driver,christopherjwang/mongo-c-driver,rcsanchez97/mongo-c-driver,ajdavis/mongo-c-driver,mongodb/mongo-c-driver,Convey-Compliance/mongo-c-driver,ajdavis/mongo-c-driver,jmikola/mongo-c-driver,remicollet/mongo-c-driver,mongodb/mongo-c-driver,remicollet/mongo-c-driver,u2yg/mongo-c-driver,bjori/mongo-c-driver,beingmeta/mongo-c-driver,derickr/mongo-c-driver,Convey-Compliance/mongo-c-driver,bjori/mongo-c-driver,acmorrow/mongo-c-driver,u2yg/mongo-c-driver,beingmeta/mongo-c-driver,malexzx/mongo-c-driver,derickr/mongo-c-driver,u2yg/mongo-c-driver,mongodb/mongo-c-driver,mschoenlaub/mongo-c-driver,bjori/mongo-c-driver,mongodb/mongo-c-driver,malexzx/mongo-c-driver,bjori/mongo-c-driver,bjori/mongo-c-driver,bjori/mongo-c-driver,ksuarz/mongo-c-driver,ac000/mongo-c-driver,beingmeta/mongo-c-driver,Convey-Compliance/mongo-c-driver,derickr/mongo-c-driver,ajdavis/mongo-c-driver,ac000/mongo-c-driver,ksuarz/mongo-c-driver,mongodb/mongo-c-driver,mschoenlaub/mongo-c-driver,derickr/mongo-c-driver,mongodb/mongo-c-driver,Convey-Compliance/mongo-c-driver,malexzx/mongo-c-driver,rcsanchez97/mongo-c-driver,rcsanchez97/mongo-c-driver,christopherjwang/mongo-c-driver,acmorrow/mongo-c-driver,ajdavis/mongo-c-driver,beingmeta/mongo-c-driver,Machyne/mongo-c-driver,ajdavis/mongo-c-driver,remicollet/mongo-c-driver,bjori/mongo-c-driver,jmikola/mongo-c-driver,rcsanchez97/mongo-c-driver,acmorrow/mongo-c-driver,remicollet/mongo-c-driver,beingmeta/mongo-c-driver,mschoenlaub/mongo-c-driver,beingmeta/mongo-c-driver,rcsanchez97/mongo-c-driver,jmikola/mongo-c-driver,jmikola/mongo-c-driver,ac000/mongo-c-driver,rcsanchez97/mongo-c-driver,Convey-Compliance/mongo-c-driver,jmikola/mongo-c-driver,acmorrow/mongo-c-driver,acmorrow/mongo-c-driver,derickr/mongo-c-driver,u2yg/mongo-c-driver,beingmeta/mongo-c-driver,ajdavis/mongo-c-driver