MDP-341 Synchronize around MongoClient creation
MDP-341 Synchronize around MongoClient creation

We share a common auth'd MongoClient across our 'Arctic' clients.
There's a race between client-creation, auth'ing and adding the
MongoClient as a member to the Arctic instance.
r0k3/arctic,Frankkkkk/arctic,manahl/arctic,Frankkkkk/arctic,r0k3/arctic