fix

Author: trask

instrumentation/grpc-1.6/library/src/main/java/io/opentelemetry/instrumentation/grpc/v1_6/GrpcRpcAttributesGetter.java

@@ -41,11 +41,17 @@ public String getMethod(GrpcRequest request) {
     String fullMethodName = request.getFullMethodName();
     int slashIndex = fullMethodName.lastIndexOf('/');
     if (slashIndex == -1) {
-      return fullMethodName;
+      return null;
     }
     return fullMethodName.substring(slashIndex + 1);
   }
 
+  @Override
+  @Nullable
+  public String getRpcMethod(GrpcRequest request) {
+    return request.getFullMethodName();
+  }
+
   @Override
   @Nullable
   public Long getRequestSize(GrpcRequest request) {