fix(B3Propagator): B3 sampled causing gRPC error (open-telemetry#977)

* fix(B3Propagator): B3 sampled causing gRPC error

* fix: review comment

Author: mayurkale22

Diff for: packages/opentelemetry-core/src/context/propagation/B3Propagator.ts

@@ -57,7 +57,13 @@ export class B3Propagator implements HttpTextPropagator {
       // We set the header only if there is an existing sampling decision.
       // Otherwise we will omit it => Absent.
       if (spanContext.traceFlags !== undefined) {
-        setter(carrier, X_B3_SAMPLED, Number(spanContext.traceFlags));
+        setter(
+          carrier,
+          X_B3_SAMPLED,
+          (TraceFlags.SAMPLED & spanContext.traceFlags) === TraceFlags.SAMPLED
+            ? '1'
+            : '0'
+        );
       }
     }
   }

Diff for: packages/opentelemetry-core/test/context/B3Propagator.test.ts

@@ -60,7 +60,7 @@ describe('B3Propagator', () => {
         'd4cda95b652f4a1592b449d5929fda1b'
       );
       assert.deepStrictEqual(carrier[X_B3_SPAN_ID], '6e0c63257de34c92');
-      assert.deepStrictEqual(carrier[X_B3_SAMPLED], TraceFlags.SAMPLED);
+      assert.deepStrictEqual(carrier[X_B3_SAMPLED], '1');
     });
 
     it('should set b3 traceId and spanId headers - ignore tracestate', () => {
@@ -82,7 +82,7 @@ describe('B3Propagator', () => {
         'd4cda95b652f4a1592b449d5929fda1b'
       );
       assert.deepStrictEqual(carrier[X_B3_SPAN_ID], '6e0c63257de34c92');
-      assert.deepStrictEqual(carrier[X_B3_SAMPLED], TraceFlags.NONE);
+      assert.deepStrictEqual(carrier[X_B3_SAMPLED], '0');
     });
 
     it('should not inject empty spancontext', () => {

Diff for: packages/opentelemetry-core/test/context/composite.test.ts

@@ -80,7 +80,7 @@ describe('Composite Propagator', () => {
 
       assert.strictEqual(carrier[X_B3_TRACE_ID], traceId);
       assert.strictEqual(carrier[X_B3_SPAN_ID], spanId);
-      assert.strictEqual(carrier[X_B3_SAMPLED], 1);
+      assert.strictEqual(carrier[X_B3_SAMPLED], '1');
       assert.strictEqual(
         carrier[TRACE_PARENT_HEADER],
         `00-${traceId}-${spanId}-01`