[2315] Minor code cleanup.

src/lib/dhcpsrv/cfgmgr.h

@@ -217,6 +217,7 @@ protected:
 private:
 
     /// A map containing option definitions for different option spaces.
+    /// The map key holds an option space name.
     std::map<std::string, OptionDefContainer> option_def_spaces_;
 };
 

src/lib/dhcpsrv/subnet.cc

@@ -62,12 +62,6 @@ Subnet::delOptions() {
     option_spaces_.clear();
 }
 
-const Subnet::OptionContainer&
-Subnet::emptyOptionContainer() {
-    static OptionContainer container;
-    return (container);
-}
-
 const Subnet::OptionContainer&
 Subnet::getOptions(const std::string& option_space) const {
     // Search the map to get the options container for the particular
@@ -78,7 +72,9 @@ Subnet::getOptions(const std::string& option_space) const {
     // has been configured for this option space yet. Thus we have to
     // return an empty container to the caller.
     if (options == option_spaces_.end()) {
-        return (emptyOptionContainer());
+        // The default constructor creates an empty container.
+        static OptionContainer container;
+        return (container);
     }
     // We found some option container for the option space specified.
     // Let's return a const reference to it.

src/lib/dhcpsrv/subnet.h

@@ -224,17 +224,6 @@ public:
     /// @brief Delete all options configured for the subnet.
     void delOptions();
 
-    /// @brief Return a reference to an empty option container.
-    ///
-    /// The empty option container is returned when no other
-    /// suitable container can be found. For example, this is
-    /// the case when trying to get a set of options for the
-    /// particular option space that has no options configured
-    /// for the subnet.
-    ///
-    /// @return reference to the empty option container.
-    static const OptionContainer& emptyOptionContainer();
-
     /// @brief checks if the specified address is in pools
     ///
     /// Note the difference between inSubnet() and inPool(). For a given