Summary: Recent patch introduced a bug that if non-mmap mode is used, in prefix encoding case, there is a resizing of cur_key_ within the same prefix, we still read prefix from the released buffer. It fails ASAN tests and this commit fixes it.
Test Plan: Run the ASAN tests for the failing test case.
Reviewers: IslamAbdelRahman, yhchiang, anthony, igor, kradhakrishnan, rven
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D47457