Fix double-sampling in event tracking

Summary:
`CacheAllocator::recordEvent()` and `BlockCache::recordEvent()` both call `eventTracker->sampleKey()` to gate entry, then call `eventTracker->record()` which internally calls `sampleKey()` again.

Fix by switching both call sites from `record()` to `recordWithoutSampling()`, since `sampleKey()` is already called by the caller. This matches the documented pattern in `EventTracker.h`: "If you want one sample call per event then consider using sampleKey + recordWithoutSampling."

Reviewed By: rlyerly

Differential Revision: D100871776

fbshipit-source-id: 3386c0b30de692a7ae3d2cf3bcd36016a26ab47d

Author: pbhandar2

cachelib/allocator/CacheAllocator.h

@@ -1865,7 +1865,7 @@ class CacheAllocator : public CacheBase {
           eventInfo.poolId = *params.poolId;
         }
 
-        eventTracker->record(eventInfo);
+        eventTracker->recordWithoutSampling(eventInfo);
       }
     } else if (auto legacyEventTracker = getLegacyEventTracker()) {
       folly::Optional<uint32_t> size =

cachelib/navy/block_cache/BlockCache.cpp

@@ -1032,7 +1032,7 @@ void BlockCache::recordEvent(folly::StringPiece key,
       }
     }
 
-    eventTracker->record(eventInfo);
+    eventTracker->recordWithoutSampling(eventInfo);
   } else if (legacyEventTracker_.has_value()) {
     legacyEventTracker_->get().record(event, key, result, size);
   }