Fix regressions from the initial pass of the upstream-hash-by annotation

[methodmissing]

References this fallout from #5:

E1003 11:49:02.768548       8 controller.go:428] unexpected failure restarting the backend: 
template: nginx.tmpl:267:23: executing "nginx.tmpl" at <$upstream.UpstreamHa...>: can't evaluate field UpstreamHashBy in type *ingress.Backend

I had to introduce special case handling for the upstream-hash-by annotation on backend creation as most of the annotations are scoped to the Location type and injected by means of the mergeLocationAnnotations utility helper.

🎩 :

host:test user$ kubectl describe ing -n something-staging
Name:            something-web
Namespace:        something-staging
Address:        X.X.X.X
Default backend:    default-http-backend:80 (Y.Y.Y.Y:8080)
TLS:
  star-something terminates something-staging.something.com
Rules:
  Host                    Path    Backends
  ----                    ----    --------
  something-staging.something.com    
                             something-web:80 (<none>)
Annotations:
  auth-realm:        blah bblah
  auth-secret:        something-basic-auth
  auth-type:        basic
  upstream-hash-by:    $request_uri <<<<<<<<<<<<<<<<<<<<<<<<<<<

    upstream something-staging-something-web-80 {
        # Load balance algorithm; empty for round robin, which is the default
        least_conn;

        hash $request_uri consistent; <<<<<<<<<<<<<<<<<<<<
        server Y.Y.Y.Y:8000 max_fails=0 fail_timeout=0;
    }

Also reasoning regarding the version:

Previous version 0.9.0-beta.12-shopify basically represents a new upstream version already available so I think this would work better: 0.9.0-beta.11-shopify-<latest-feature-added>
then the version lines up with the last upstream version we're tracking
and hint @ the shopify fork and also the last feature added
eg. 0.9.0-beta.11-shopify-upstream-hash-by

@ibawt @n1koo @mkobetic @karanthukral

[karanthukral]

LGTM!