Relaxed assert in forward iterator

Summary:
It looks like in some cases an assert in SeekInternal failed when computing the
hints for the next level because user_key was the same as the largest key and
not strictly smaller. Relaxing the assert to expect smaller or equal keys.

Test Plan: make clean all check

Reviewers: sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D46443

db/forward_iterator.cc

@@ -335,7 +335,7 @@ void ForwardIterator::SeekInternal(const Slice& internal_key,
           int cmp_smallest = user_comparator_->Compare(
               user_key, level_files[f_idx]->smallest.user_key());
           assert(user_comparator_->Compare(
-                     user_key, level_files[f_idx]->largest.user_key()) < 0);
+                     user_key, level_files[f_idx]->largest.user_key()) <= 0);
           indexer.GetNextLevelIndex(level, f_idx, cmp_smallest, -1,
                                     &search_left_bound, &search_right_bound);
         } else {