[RocksDB] Fix binary search while finding probable wal files

Summary:
RocksDB does a binary search to look at the files which might contain the requested sequence number at the call GetUpdatesSince.
There was a bug in the binary search => when the file pointed by the middle index of bsearch was empty/corrupt it needst to resize the vector and update indexes.
This now fixes that.

Test Plan: existing unit tests pass.

Reviewers: heyongqiang, dhruba

Reviewed By: heyongqiang

CC: leveldb

Differential Revision: https://reviews.facebook.net/D9777

db/db_impl.cc

@@ -934,9 +934,7 @@ Status DBImpl::FindProbableWALFiles(std::vector<LogFile>* const allLogs,
     if (!s.ok()) {
       if (CheckFileExistsAndEmpty(allLogs->at(mid))) {
         allLogs->erase(allLogs->begin() + mid);
-        if (mid == start) {
-          ++start;
-        }
+        --end;
         continue;
       }
       return s;