* Throw away result of multierror.Append
When given a *multierror.Error, it is mutated, therefore the return
value is not needed.
* Simplify MergeMultierrorWarnings, use StringBuilder
* Hash.Write() never returns an error
* Remove error that was always nil
* Remove error from Resources.Add signature
When this was originally written it could return an error, but that was
refactored away, and callers of it as of today never handle the error.
* Throw away results of io.Copy during Bridge
* Handle errors when computing node class in test
In a few places Nomad was using flag implementations directly
from Consul, lending to Nomad's need to import consul. Replace
those uses with helpers already in Nomad, and copy over the bare
minimum needed to make the autopilot flags behave as they have.