nightly: use shutil.move() only so all ops work across filesystems

fdroid/fdroidserver!377 (comment 49998712)
2 jobs for nightly-fixes in 42 minutes and 1 second (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #43156128
metadata_v0

00:04:07

passed #43156127
test

00:42:01