ibm-read-vpd: Switch to the right symlinked JSON

This commit:
* Makes the VPD parser use the symlinked JSON if one is setup.
  For example via a system VPD service.
* Makes the vpd-tool and vpd-manager use the symlinked JSON.

Signed-off-by: Santosh Puranik <santosh.puranik@in.ibm.com>
Change-Id: Id7f845e02917e3a66d1fa9754da71ed0005c0cb8
diff --git a/vpd-manager/manager.cpp b/vpd-manager/manager.cpp
index a313e86..9eeb6e2 100644
--- a/vpd-manager/manager.cpp
+++ b/vpd-manager/manager.cpp
@@ -48,7 +48,7 @@
 
 void Manager::processJSON()
 {
-    std::ifstream json(INVENTORY_JSON, std::ios::binary);
+    std::ifstream json(INVENTORY_JSON_SYM_LINK, std::ios::binary);
 
     if (!json)
     {