Fixed compile errors due to some gcc does not have std::map::emplace

Fixed compile errors due to some gcc does not have std::map::emplace

Summary:
Fixed the following compile errors due to some gcc does not have std::map::emplace

util/thread_status_impl.cc: In static member function ‘static std::map<std::basic_string<char>, long unsigned int> rocksdb::ThreadStatus::InterpretOperationProperties(rocksdb::ThreadStatus::OperationType, const uint64_t*)’:
util/thread_status_impl.cc:88:20: error: ‘class std::map<std::basic_string<char>, long unsigned int>’ has no member named ‘emplace’
util/thread_status_impl.cc:90:20: error: ‘class std::map<std::basic_string<char>, long unsigned int>’ has no member named ‘emplace’
util/thread_status_impl.cc:94:20: error: ‘class std::map<std::basic_string<char>, long unsigned int>’ has no member named ‘emplace’
util/thread_status_impl.cc:96:20: error: ‘class std::map<std::basic_string<char>, long unsigned int>’ has no member named ‘emplace’
util/thread_status_impl.cc:98:20: error: ‘class std::map<std::basic_string<char>, long unsigned int>’ has no member named ‘emplace’
util/thread_status_impl.cc:101:20: error: ‘class std::map<std::basic_string<char>, long unsigned int>’ has no member named ‘emplace’
make: *** [util/thread_status_impl.o] Error 1

Test Plan: make db_bench

Reviewers: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D38643