Revert "If we are opening a local minimongo collection, and are not defined as the client, then the server can be null, but we should still be able to connect to a local minimongo db.There are not any cases where the conenction is null, where we would want to proceed."

This reverts commit 94f5efc893a482dc82472e3ce09ffd38b2e06363.

That commit is good but somewhat incomplete because there are two other
places in collection.js that do comparisons against
Meteor.server. Rather than put the time in now to get it perfect, we're
just going to not use *named* Meteor.Collections in a non-webapp server
program for now.
some XXX comments about Meteor.server === null