kv: silence the gcc warning of func foo was hidden

this silences the warnings like

ceph/ceph/src/kv/KeyValueDB.h:59:18: warning: ‘virtual void
KeyValueDB::TransactionImpl::set(const string&, const char*, size_t,
const bufferlist&)’ was hidden [-Woverloaded-\
virtual]
     virtual void set(
                  ^~~

Signed-off-by: Kefu Chai <kchai@redhat.com>

src/kv/LevelDBStore.h

@@ -190,12 +190,14 @@ class LevelDBStore : public KeyValueDB {
       const string &prefix,
       const string &k,
       const bufferlist &bl);
+    using KeyValueDB::TransactionImpl::set;
     void rmkey(
       const string &prefix,
       const string &k);
     void rmkeys_by_prefix(
       const string &prefix
       );
+    using KeyValueDB::TransactionImpl::rmkey;
   };
 
   KeyValueDB::Transaction get_transaction() {
@@ -213,7 +215,9 @@ class LevelDBStore : public KeyValueDB {
   int get(const string &prefix, 
     const string &key,   
     bufferlist *value);
-
+
+  using KeyValueDB::get;
+
   class LevelDBWholeSpaceIteratorImpl :
     public KeyValueDB::WholeSpaceIteratorImpl {
   protected:

src/kv/MemDB.h

@@ -86,7 +86,9 @@ class MemDB : public KeyValueDB
 
     void set(const std::string &prefix, const std::string &key,
       const bufferlist &val);
+    using KeyValueDB::TransactionImpl::set;
     void rmkey(const std::string &prefix, const std::string &k);
+    using KeyValueDB::TransactionImpl::rmkey;
     void rmkeys_by_prefix(const std::string &prefix);
 
     void merge(const std::string &prefix, const std::string &key, const bufferlist  &value);
@@ -127,11 +129,13 @@ class MemDB : public KeyValueDB
   int submit_transaction_sync(Transaction);
 
   int get(const std::string &prefix, const std::set<std::string> &key,
-    std::map<std::string, bufferlist> *out);
+    std::map<std::string, bufferlist> *out) override;
 
   int get(const std::string &prefix, const std::string &key,
           bufferlist *out) override;
 
+  using KeyValueDB::get;
+
   class MDBWholeSpaceIteratorImpl : public KeyValueDB::WholeSpaceIteratorImpl {
 
       mdb_iter_t m_iter;