Delete local sv when destroying DB from stress test

Summary: Not deleting local SV caused some an crash test issue: http://ci-builds.fb.com/job/rocksdb_asan_crash_test/83/console

Test Plan: ran unit tests

Reviewers: ljin

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16635

db/db_impl.cc

@@ -402,6 +402,15 @@ void DBImpl::TEST_Destroy_DBImpl() {
          bg_logstats_scheduled_) {
     bg_cv_.Wait();
   }
+  mutex_.Unlock();
+
+  // Release SuperVersion reference kept in ThreadLocalPtr.
+  // This must be done outside of mutex_ since unref handler can lock mutex.
+  // It also needs to be done after FlushMemTable, which can trigger local_sv_
+  // access.
+  delete local_sv_;
+
+  mutex_.Lock();
   if (super_version_ != nullptr) {
     bool is_last_reference __attribute__((unused));
     is_last_reference = super_version_->Unref();