udevd: event - make db loading lazy in REMOVE event handling

We were explicitly eagerly loading the db, then deletenig the backing file and then processing the
rules/symlinks. Instead we delete the backnig db file as the last step and let the db loading be
lazy as everywhere else.

This may save us a bit of work in casese where the db is not needed, but more importantly it hides
some implementation details of libudev-device form udevd.