Nearly each tests gets a fresh store (in the test root residing under TMPDIR),
which with default settings means 8 MiB of reserved space to be deleted by the
user in case of space shortages, which of course for a test suite is just
wasted. Stop doing that to considerably reduce the litter (experimentally, from
3.7 GiB to 67 MiB per run). The old functional test suite already did the same.
Change-Id: I912cdda6e796ea37cfee0b8fe0478e976a6a6964