Disable RejectInsecureRequest middleware on unix sockets

[jayme-github]

Proposed changes

RejectInsecureRequests handler fails for requests via socket because the remote address is @.
We should not reject insecure requests coming in via unix socket as there is no TLS support anyways.

{"error":"address @: missing port in address","level":"warning","msg":"Could not serve http connection","time":"2019-01-16T08:39:17Z"}
{"code":502,"details":{},"error":"Can not serve request over insecure http","level":"error","msg":"An error occurred while handling a request","reason":"","request-id":"","status":"","time":"2019-01-16T08:39:17Z", "trace":"
Stack trace: 
github.com/ory/hydra/cmd/server.(*Handler).RejectInsecureRequests
        /go/src/github.com/ory/hydra/cmd/server/handler.go:303
github.com/ory/hydra/cmd/server.(*Handler).RejectInsecureRequests-fm
        /go/src/github.com/ory/hydra/cmd/server/handler.go:62
github.com/urfave/negroni.HandlerFunc.ServeHTTP
        /go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:29
github.com/urfave/negroni.middleware.ServeHTTP
        /go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38
github.com/urfave/negroni.middleware.ServeHTTP-fm
        /go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38
github.com/ory/x/metricsx.(*MetricsManager).ServeHTTP
        /go/pkg/mod/github.com/ory/x@v0.0.33/metricsx/middleware.go:207
github.com/urfave/negroni.middleware.ServeHTTP
        /go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38
github.com/urfave/negroni.middleware.ServeHTTP-fm
        /go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38
github.com/ory/hydra/metrics/prometheus.(*MetricsManager).ServeHTTP
        /go/src/github.com/ory/hydra/metrics/prometheus/middleware.go:26
github.com/urfave/negroni.middleware.ServeHTTP
        /go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38
github.com/urfave/negroni.middleware.ServeHTTP-fm
        /go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38
github.com/meatballhat/negroni-logrus.(*Middleware).ServeHTTP
        /go/pkg/mod/github.com/meatballhat/negroni-logrus@v0.0.0-20170801195057-31067281800f/middleware.go:136
github.com/urfave/negroni.middleware.ServeHTTP
        /go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38
github.com/urfave/negroni.(*Negroni).ServeHTTP
        /go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:96
github.com/gorilla/context.ClearHandler.func1
        /go/pkg/mod/github.com/gorilla/context@v1.1.1/context.go:141
net/http.HandlerFunc.ServeHTTP
        /usr/local/go/src/net/http/server.go:1964
net/http.serverHandler.ServeHTTP
        /usr/local/go/src/net/http/server.go:2741
net/http.(*conn).serve
        /usr/local/go/src/net/http/server.go:1847
runtime.goexit
        /usr/local/go/src/runtime/asm_amd64.s:1333

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  vulnerability, I confirm that I got green light (please contact hi@ory.sh) from the maintainers to push the changes.
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• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation within the code base (if appropriate)
• I have documented my changes in the developer guide (if appropriate)

[aeneasr]

Thank you!