Inspect auth failures to see if we should actually just retry.

We got this error during a failover tonight:

> Uncaught exception in the API: #<Moped::Errors::AuthenticationFailure: The operation: #<Moped::Protocol::Commands::Authenticate
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:    @length=151
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:    @request_id=3
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:    @response_to=0
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:    @op_code=2004
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:    @flags=[]
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:    @full_collection_name="uo_users.$cmd"
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:    @skip=0
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:    @limit=-1
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:    @selector={:authenticate=>1, :user=>"REDACTED", :nonce=>"X", :key=>"Y"}
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:    @fields=nil>
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:  failed with error 10009: "exception: ReplicaSetMonitor no master found for set: 42a61b38226d9f4a3bdeef465b616eb7"
Jul 02 19:13:43 api-app-prd-iad-cld-08 production.log:  See https://github.com/mongodb/mongo/blob/master/docs/errors.md