Remove sleep that waits for slab advising workers

Summary:
Even though this test looks [healthy on TestX](https://www.internalfb.com/intern/test/844425196455282) it's marked flaky.  Here are the errors:
{F1988281045}

The issue seems to be that we're waiting 5 seconds for locking/advising, but sometimes the process hasn't finished by the time we get to the asserts.  That jives with this issue showing up in stress runs (18 jobs) on the dev (slow) builds.

Use the ASSERT_EVENTUALLY_TRUE helper instead.  While it internally does sleeping, it's more robust to these sorts of transient issues.

Also remove an unused header.

___

overriding_review_checks_triggers_an_audit_and_retroactive_review
Oncall Short Name: cachelib

Differential Revision: D100989998

fbshipit-source-id: 01d4c98fe4ea5dbcb6e3cbc6eb0e93b5293b06d7

Author: rlyerly

cachelib/allocator/memory/tests/SlabAllocatorTest.cpp

@@ -646,7 +646,6 @@ void testAdvise(SlabAllocator& s,
                 const size_t numAdviseSlabs,
                 void* memory,
                 const size_t size) {
-  ASSERT_EQ(util::getNumResidentPages(memory, size), util::getNumPages(size));
   auto memRssBefore = facebook::cachelib::util::getRSSBytes();
 
   // Use up all but a few slabs so that we have a few free
@@ -672,8 +671,6 @@ void testRestoreAndAdvise(SlabAllocator& s,
                           const size_t numAdviseSlabs,
                           void* memory,
                           const size_t size) {
-  ASSERT_EQ(util::getNumResidentPages(memory, size),
-            util::getNumPages(size - numAdviseSlabs * Slab::kSize));
   auto memRssBefore = facebook::cachelib::util::getRSSBytes();
 
   // No free slabs available
@@ -720,17 +717,20 @@ TEST_F(SlabAllocatorTest, AdviseSaveRestore) {
   {
     SlabAllocator s(memory, size, config);
     // Wait until memory locking completes.
-    /* sleep override */
-    std::this_thread::sleep_for(std::chrono::seconds(5));
+    ASSERT_EVENTUALLY_TRUE([=]() {
+      return util::getNumResidentPages(memory, size) == util::getNumPages(size);
+    });
     testAdvise(s, numSlabs, numAdviseSlabs, memory, size);
     state = s.saveState();
   }
 
   {
     SlabAllocator r(state, memory, size, config);
     // Wait until memory locking completes.
-    /* sleep override */
-    std::this_thread::sleep_for(std::chrono::seconds(5));
+    ASSERT_EVENTUALLY_TRUE([=]() {
+      return util::getNumResidentPages(memory, size) ==
+             util::getNumPages(size - numAdviseSlabs * Slab::kSize);
+    });
     testRestoreAndAdvise(r, numAdviseSlabs, memory, size);
   }
 }

cachelib/common/TestUtils.h

@@ -18,7 +18,6 @@
 
 #include <cstdint>
 #include <functional>
-#include <set>
 #include <string>
 
 namespace facebook {