remove destructor, close environment only once

Author: ziollek

src/collection/backend/lmdb.cc

@@ -40,11 +40,6 @@ namespace backend {
 LMDB::LMDB(std::string name) :
     Collection(name), m_env(NULL), isOpen(false) {}
 
-
-LMDB::~LMDB() {
-    mdb_env_close(m_env);
-}
-
 int LMDB::txn_begin(unsigned int flags, MDB_txn **ret) {
     if (!isOpen) {
         MDBEnvProvider* provider = MDBEnvProvider::GetInstance();

src/collection/backend/lmdb.h

@@ -99,7 +99,6 @@ class LMDB :
     public Collection {
  public:
     explicit LMDB(std::string name);
-    ~LMDB();
     void store(std::string key, std::string value) override;
 
     bool storeOrUpdateFirst(const std::string &key,