minor: don't preallocate for replica set tests
minor: don't preallocate for replica set tests

jonhyman/mongo-ruby-driver,tommyb67/mongo-ruby-driver,estolfo/mongo-ruby-driver,mongodb/mongo-ruby-driver,kay-kim/mongo-ruby-driver,0x00evil/mongo-ruby-driver,pcarrier-packaging/deb-ruby-mongo,pcarrier-packaging/deb-ruby-mongo,jonhyman/mongo-ruby-driver,brandonblack/mongo-ruby-driver,ShanaLMoore/mongo-ruby-driver,namusyaka/mongo-ruby-driver,fhwang/mongo-ruby-driver,pcarrier-packaging/deb-ruby-mongo,saghm/mongo-ruby-driver,mongodb/mongo-ruby-driver,mongodb/mongo-ruby-driver,kay-kim/mongo-ruby-driver,aherlihy/mongo-ruby-driver,AndyObtiva/mongo-ruby-driver,wandenberg/mongo-ruby-driver,saghm/mongo-ruby-driver,fairplace/mongo-ruby-driver,estolfo/mongo-ruby-driver,pcarrier-packaging/deb-ruby-mongo,dunedain289/mongo-ruby-driver,pcarrier-packaging/deb-ruby-mongo,agis-/mongo-ruby-driver,xronos-i-am/mongo-ruby-driver