Currently, we configure LimitNOFILE on scylla-server.service, but we
don't configure fs.nr_open and fs.file-max.
When fs.nr_open or fs.file-max are smaller than LimitNOFILE, we may fail
to allocate FDs.
To fix this issue, raise fs.file-max and fs.nr_open to enogh size for
scylla.
Fixes#9461Closes#9461
06c28585f9