install.sh: apply sysctl.d files on non-packaging installation
install.sh: apply sysctl.d files on non-packaging installation

We don't apply sysctl.d files on non-packaging installation, apply them
just like rpm/deb taking care of that.

Fixes #7702

Closes #7705

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla