Expose name of tracing and fix install batch issue

Previously the tracing service name was defaulted to rust.dora which
prevented some functionalities of Jaeger tracing.

There were also issues with pushing traces as batch as see here: https://github.com/open-telemetry/opentelemetry-rust/issues/674

tracing/src/lib.rs

@@ -38,12 +38,12 @@ impl<'a> Extractor for MetadataMap<'a> {
 ///
 /// TODO: Make Jaeger configurable
 ///
-pub fn init_tracing() -> Result<sdktrace::Tracer, TraceError> {
+pub fn init_tracing(name: &str) -> Result<sdktrace::Tracer, TraceError> {
     global::set_text_map_propagator(TraceContextPropagator::new());
     opentelemetry_jaeger::new_pipeline()
         .with_agent_endpoint("172.17.0.1:6831")
-        .with_service_name("rust.dora")
-        .install_batch(opentelemetry::runtime::Tokio)
+        .with_service_name(name)
+        .install_simple()
 }
 
 pub fn serialize_context(context: &Context) -> String {