We have a few tests that try to set image_creation_threshold, but it
didn't actually have any effect because we were missing some critical
code to load the setting from config file into memory.
The two modified tests in `test_remote_storage.py perform
compaction and GC, and assert that GC removes some layers. That
only happens if new image layers are created by the
compaction. The tests explicitly disabled image layer creation by
setting image_creation_threshold to a high value, but it didn't
take effect because reading image_creation_threshold from config
file was broken, which is why the test worked. Fix the test to
set image_creation_threshold low, instead, so that GC has work to
do.
Change 'test_tenant_conf.py' so that it exercises the added code.
This might explain why we're apparently missing test coverage for GC
(issue #3415), although I didn't try to address that here, nor did I
check if this improves the it.
fb1581d0b9