objectManager: correct other invalid index code in onNameVanished

objectManager: correct other invalid index code in onNameVanished

The object manager tries to synthesize interface removal
events if the bus name of a remote object drops off the bus.

The code had bad typos in it, though: it reuses the `i`
index variable in its inner loop, where it should be using
the `j` index variable.

This commit corrects the i/j confusion.