tests: row_cache_test: Induce update failure more reliably
tests: row_cache_test: Induce update failure more reliably

After changing region evicitability condition to be less strict, cache
update stopped failing because reclamation was able to compact dense
region. Induce failure by installing evictor which refuses to evict
from cache beyond few elements.

avikivity/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,scylladb/scylla,duarten/scylla