Fixed unit test c_test by initializing logger=NULL.

Summary:
Fixed unit test c_test by initializing logger=NULL.

Removed "atomic" from last_log_ts so that unit tests do not require C11 compiler.
Anyway, last_log_ts is mostly used for logging, so it is ok if it is loosely
accurate.

Test Plan: run c_test

Reviewers: heyongqiang

Reviewed By: heyongqiang

Differential Revision: https://reviews.facebook.net/D4803

db/db_impl.cc

@@ -134,7 +134,8 @@ DBImpl::DBImpl(const Options& options, const std::string& dbname)
       log_(NULL),
       tmp_batch_(new WriteBatch),
       bg_compaction_scheduled_(false),
-      manual_compaction_(NULL) {
+      manual_compaction_(NULL),
+      logger_(NULL) {
   mem_->Ref();
   has_imm_.Release_Store(NULL);
 

db/db_impl.h

@@ -7,7 +7,6 @@
 
 #include <deque>
 #include <set>
-#include <atomic>
 #include "db/dbformat.h"
 #include "db/log_writer.h"
 #include "db/snapshot.h"
@@ -187,7 +186,7 @@ class DBImpl : public DB {
 
   StatsLogger* logger_;
 
-  std::atomic<int64_t> last_log_ts;
+  int64_t volatile last_log_ts;
 
   // Per level compaction stats.  stats_[level] stores the stats for
   // compactions that produced data for the specified "level".