Respect environment variables when creating internal tracer (#6179)

## Which problem is this PR solving?
Resolves #6122 

## Description of the changes
- The changes include using the `otlptracegrpc.WithInsecure()` based on
`OTEL_EXPORTER_OTLP_ENDPOINT` and `OTEL_EXPORTER_OTLP_INSECURE` env
variables.

## Checklist
- [x] I have read
https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
- [x] I have signed all commits
- [ ] I have added unit tests for the new functionality
- [ ] I have run lint and test steps successfully
  - for `jaeger`: `make lint test`
  - for `jaeger-ui`: `yarn lint` and `yarn test`

---------

Signed-off-by: Alok Kumar Singh <[email protected]>

pkg/jtracer/jtracer.go

@@ -5,6 +5,8 @@ package jtracer
 
 import (
 	"context"
+	"os"
+	"strings"
 	"sync"
 
 	"go.opentelemetry.io/otel"
@@ -109,9 +111,17 @@ func otelResource(ctx context.Context, svc string) (*resource.Resource, error) {
 	)
 }
 
+func defaultGRPCOptions() []otlptracegrpc.Option {
+	var options []otlptracegrpc.Option
+	if !(strings.HasPrefix(os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT"), "https://") || strings.ToLower(os.Getenv("OTEL_EXPORTER_OTLP_INSECURE")) == "false") {
+		options = append(options, otlptracegrpc.WithInsecure())
+	}
+	return options
+}
+
 func otelExporter(ctx context.Context) (sdktrace.SpanExporter, error) {
 	client := otlptracegrpc.NewClient(
-		otlptracegrpc.WithInsecure(),
+		defaultGRPCOptions()...,
 	)
 	return otlptrace.New(ctx, client)
 }