Move setting the priority U-Boot variable to ubi

The service that sets the priority value is unique to the ubi
layout because there is only one version at a time on the
static layout.
Move the calling of the service to the ubi implementation.

Tested:
- Witherspoon: Priorities are still set.
- Romulus: The BMC.Updater app does not core dump with the
latest sdbusplus changes due to calling a non-existent service.

Change-Id: Ica1c68f00d5cb43c51ee09c5a3851613edf941d5
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/item_updater.cpp b/item_updater.cpp
index 1bbf200..22734ef 100644
--- a/item_updater.cpp
+++ b/item_updater.cpp
@@ -356,6 +356,12 @@
     return ItemUpdater::ActivationStatus::ready;
 }
 
+void ItemUpdater::savePriority(const std::string& versionId, uint8_t value)
+{
+    storeToFile(versionId, value);
+    helper.setEntry(versionId, value);
+}
+
 void ItemUpdater::freePriority(uint8_t value, const std::string& versionId)
 {
     std::map<std::string, uint8_t> priorityMap;