disable defragment-memory-on-idle-by-default
disable defragment-memory-on-idle-by-default

It's been linked with various performance issues, either by causing
them or making them worse. One example is #1634, and also recently
I have investigated continuous performance degradation that was also
linked to defrag on idle activity.

Until we can figure out how to reduce its impact, we should disable it.

Signed-off-by: Glauber Costa <7ba9037b0dd006f9408bd45b94707becd5cd4e87@glauber.scylladb>
Message-Id: <ee9b6abbb6af6b5f85ab32de9f3d32d331920950@scylladb.com>

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