Update functions from umount2 to Unmount_by_Path

Change-Id: Ib701c1002ceccfef222424941aa55e13a290d996
diff --git a/gui/action.cpp b/gui/action.cpp
index 047dc62..e069c0f7 100755
--- a/gui/action.cpp
+++ b/gui/action.cpp
@@ -1948,7 +1948,7 @@
 				// PartitionManager failed to unmount /vendor, this should not happen,
 				// but in case it does, do a lazy unmount
 				LOGINFO("WARNING: vendor partition could not be unmounted normally!\n");
-				umount2("/vendor", MNT_DETACH);
+				PartitionManager.UnMount_By_Path("/vendor", false, MNT_DETACH);
 			}
 		}
 		PartitionManager.Set_Active_Slot(arg);