[Bug]: `config.Configuration.InitGlobalTracer` panics if `http.DefaultTransport` is not a `*http.Transport`

[colega]

What happened?

I called config.Configuration.InitGlobalTracer(...) after replacing the http.DefaultTransport with a custom implementation, and it panicked.

The code assumes that http.DefaultTransport is a *http.Transport, and panics otherwise:

jaeger-client-go/sampler_remote.go

Line 308 in 8d8e8fc

customTransport := http.DefaultTransport.(*http.Transport).Clone()

Steps to reproduce

1. Replace http.DefaultTransport value in your app.
2. Call config.Configuration.InitGlobalTracer()

Example: https://go.dev/play/p/TH-uFyyMuLD

package main

import (
	"fmt"
	"net/http"

	"github.com/uber/jaeger-client-go/config"
)

func main() {
	http.DefaultTransport = &customTransport{&http.Transport{}}
	closer, err := config.Configuration{}.InitGlobalTracer("hello-world")
	if err != nil {
		panic(fmt.Errorf("failed: %w", err))
	}
	defer closer.Close()

	fmt.Println("Hello, 世界")
}

type customTransport struct {
	next http.RoundTripper
}

func (ct *customTransport) RoundTrip(req *http.Request) (*http.Response, error) {
	return ct.next.RoundTrip(req)
}

Expected behavior

It shouldn't panic.

Relevant log output

No response

Screenshot

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Additional context

No response

Jaeger backend version

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SDK

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Pipeline

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Stogage backend

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Operating system

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Deployment model

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Deployment configs

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