Refactor: remove DeleteAll interface

There is no need for ItemUpdater to implement DeleteAll interface,
remove it.

Also make Activation::versionId private and provide a public
getVersionId() method;
Make ItemUpdater::erase() to pass const reference.

Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: Ifd6c61fc21b2967d6c83f1df7aaa3b2e94cae86c
diff --git a/src/activation.hpp b/src/activation.hpp
index b46105b..7ad03c9 100644
--- a/src/activation.hpp
+++ b/src/activation.hpp
@@ -128,7 +128,7 @@
                Status activationStatus, const AssociationList& assocs,
                AssociationInterface* associationInterface) :
         ActivationInherit(bus, path.c_str(), true),
-        versionId(versionId), bus(bus), path(path),
+        bus(bus), path(path), versionId(versionId),
         systemdSignals(
             bus,
             sdbusRule::type::signal() + sdbusRule::member("JobRemoved") +
@@ -171,8 +171,11 @@
     RequestedActivations
         requestedActivation(RequestedActivations value) override;
 
-    /** @brief Version id */
-    std::string versionId;
+    /** @brief Get the version ID */
+    const std::string& getVersionId() const
+    {
+        return versionId;
+    }
 
   private:
     /** @brief Check if systemd state change is relevant to this object
@@ -226,6 +229,9 @@
     /** @brief Persistent DBus object path */
     std::string path;
 
+    /** @brief Version id */
+    std::string versionId;
+
     /** @brief Used to subscribe to dbus systemd signals */
     sdbusplus::bus::match_t systemdSignals;