run-command: invalidate lstat cache after a command finished

run-command: invalidate lstat cache after a command finished

In the previous commit, we intercepted calls to `rmdir()` to invalidate
the lstat cache in the successful case, so that the lstat cache could
not have the idea that a directory exists where there is none.

The same situation can arise, of course, when a separate process is
spawned (most notably, this is the case in `submodule_move_head()`).
Obviously, we cannot know whether a directory was removed in that
process, therefore we must invalidate the lstat cache afterwards.

Note: in contrast to `lstat_cache_aware_rmdir()`, we invalidate the
lstat cache even in case of an error: the process might have removed a
directory and still have failed afterwards.

Co-authored-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>