tests/strategies: Fix in-memory storage reference in some filters
tests/strategies: Fix in-memory storage reference in some filters

As tests data are reseted between each test run, reference to in-memory storage
must be retrieved in strategy filter implementation to ensure the right one is
used.

SoftwareHeritage/swh-web-ui,SoftwareHeritage/swh-web-ui,SoftwareHeritage/swh-web-ui