Revert "Avoid set/onset calls while shallow copying RequestContext"

Summary: This added significant cost, it will take effort to deploy, reverting for now

Differential Revision: D9007024

fbshipit-source-id: 04074b09a1a2b7f9b57e3d755a2754657dda21c2

folly/io/async/Request.cpp

@@ -131,9 +131,13 @@ std::shared_ptr<RequestContext> RequestContext::setContext(
   auto& curCtx = getStaticContext();
   if (ctx != curCtx) {
     FOLLY_SDT(folly, request_context_switch_before, curCtx.get(), ctx.get());
-    get()->onUnset();
+    if (curCtx) {
+      curCtx->onUnset();
+    }
     std::swap(ctx, curCtx);
-    get()->onSet();
+    if (curCtx) {
+      curCtx->onSet();
+    }
   }
   return ctx;
 }

folly/io/async/test/RequestContextTest.cpp

@@ -126,8 +126,9 @@ TEST(RequestContext, defaultContext) {
     EXPECT_FALSE(hasData());
   }
   EXPECT_EQ(10, getData().data_);
-  EXPECT_EQ(2, getData().set_);
-  EXPECT_EQ(1, getData().unset_);
+  // TODO: should be 2/1
+  EXPECT_EQ(1, getData().set_);
+  EXPECT_EQ(0, getData().unset_);
 }
 
 TEST(RequestContext, setIfAbsentTest) {