item_updater: Use the Common.FilePath.Path to find the image files

The image manager implements the Common.FilePath.Path interface,
make use of it to find the image files instead of hardcoding the
path, since the updater shouldn't know/care where the images are.

Change-Id: Ie9ec5982af1ec2ddd6d7a1b9e69d518520225ab5
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/item_updater.hpp b/item_updater.hpp
index 97f5005..82df3e7 100755
--- a/item_updater.hpp
+++ b/item_updater.hpp
@@ -60,11 +60,11 @@
         /**
          * @brief Validates the presence of SquashFS iamge in the image dir.
          *
-         * @param[in]  versionId - The software version ID.
+         * @param[in]  filePath - The path to the SquashfFS image.
          * @param[out] result    - 0 --> if validation was successful
          *                       - -1--> Otherwise
          */
-        static int validateSquashFSImage(const std::string& versionId);
+        static int validateSquashFSImage(const std::string& filePath);
 
         /** @brief Persistent sdbusplus DBus bus connection. */
         sdbusplus::bus::bus& bus;