fix(allocation): fix ut

test=develop

Author: reyoung

paddle/fluid/memory/allocation/allocator.cc

@@ -36,7 +36,12 @@ void Allocator::Free(Allocation* allocation) { delete allocation; }
 const char* BadAlloc::what() const noexcept { return msg_.c_str(); }
 
 void AllocationDeleter::operator()(Allocation* allocation) const {
-  allocation->allocator()->Free(allocation);
+  auto* allocator = allocation->allocator();
+  if (allocator) {
+    allocator->Free(allocation);
+  } else {
+    delete allocation;  // Compatible for legacy allocation.
+  }
 }
 
 }  // namespace allocation

paddle/fluid/memory/allocation/buffered_allocator.cc

@@ -41,6 +41,7 @@ void BufferedAllocator::FreeCache(size_t size) {
   while (!allocations_.empty()) {  // free the largest
     auto it = --allocations_.end();
     cur += it->second->size();
+    delete it->second.release();
     allocations_.erase(it);
     if (cur >= size) return;
   }