Revert "[2209] Interface of the getCachedZoneWriter()"

This reverts commit 812392465ae1ffa4a583186fd48f4c7aff1640dd.

This should have gone to a branch, not to master. Reverting it until it
gets reviewed properly.

src/lib/datasrc/client_list.h

@@ -43,7 +43,6 @@ typedef boost::shared_ptr<DataSourceClientContainer>
 // and hide real definitions except for itself and tests.
 namespace memory {
 class InMemoryClient;
-class ZoneWriter;
 }
 
 /// \brief The list of data source clients.
@@ -290,31 +289,6 @@ public:
     ///      the original data source no longer contains the cached zone.
     ReloadResult reload(const dns::Name& zone);
 
-    /// \brief Return value of getCachedZoneWriter()
-    ///
-    /// A pair containing status and the zone writer, for the
-    /// getCachedZoneWriter() method.
-    typedef std::pair<ReloadResult, boost::shared_ptr<memory::ZoneWriter> >
-        ZoneWriterPair;
-
-    /// \brief Return a zone writer that can be used to reload a zone.
-    ///
-    /// This looks up a cached copy of zone and returns the ZoneWriter
-    /// that can be used to reload the content of the zone. This can
-    /// be used instead of reload() -- reload() works synchronously, which
-    /// is not what is needed every time.
-    ///
-    /// \param zone The origin of the zone to reload.
-    /// \return The result has two parts. The first one is a status describing
-    ///     if it worked or not (and in case it didn't, also why). If the status
-    ///     is ZONE_RELOADED, the second part contains a shared pointer to the
-    ///     writer. If the status is anything else, the second part is NULL.
-    /// \throw DataSourceError or anything else that the data source
-    ///      containing the zone might throw is propagated.
-    /// \throw DataSourceError if something unexpected happens, like when
-    ///      the original data source no longer contains the cached zone.
-    ZoneWriterPair getCachedZoneWriter(const dns::Name& zone);
-
     /// \brief Implementation of the ClientList::find.
     virtual FindResult find(const dns::Name& zone,
                             bool want_exact_match = false,