WiredTigerRecordStore::insertRecord doesn't need to use shared_array

buf isn't shared so scoped_array can be used in place of shared_array and avoid the overhead from reference counting.

StatusWith<RecordId>
WiredTigerRecordStore::insertRecord( OperationContext* txn,
const DocWriter* doc,
bool enforceQuota )

{ const int len = doc->documentSize(); boost::shared_array<char> buf( new char[len] ); doc->writeDocument( buf.get() ); return insertRecord( txn, buf.get(), len, enforceQuota ); }