Make callbacks to be executed in right domain

When command is executed through non executed commands queue,
callbacks are executed in wrong domain. Fix this.
Fixes for issues where mongos is not correctly removing  before passing it to the shard
Merge branch '1.4' of github.com:anton-kotenko/node-mongodb-native into anton-kotenko-1.4
Merge branch 'anton-kotenko-1.4' into 1.4