Fix authentication issue on MongoDB 2.4
Fix authentication issue on MongoDB 2.4

cchantep/ReactiveMongo,maxime-gautre/ReactiveMongo,bfil/ReactiveMongo,charleskubicek/ReactiveMongo,ornicar/ReactiveMongo,ReactiveMongo/ReactiveMongo,maxime-gautre/ReactiveMongo,mcveat/ReactiveMongo,reactific/ReactiveMongo,lunatech-labs/lunatech-reactivemongo,maowug/ReactiveMongo,ornicar/ReactiveMongo,ReactiveMongo/ReactiveMongo,sh1ng/ReactiveMongo,charleskubicek/ReactiveMongo,maowug/ReactiveMongo,cchantep/ReactiveMongo,viktortnk/ReactiveMongo,avdv/ReactiveMongo,mcveat/ReactiveMongo,avdv/ReactiveMongo,viktortnk/ReactiveMongo