Added `elasticsearch.skip_restart_on_update` attribute

Setting the attribute to `true` will skip restarts via Chef notifications.

Related: #149, #122
FIXUP `node.elasticsearch[:skip_restart_on_update]`
Changed, that `elasticsearch.skip_restart_on_update` is set to true when using "elasticsearch::search_discovery"

When using the "elasticsearch::search_discovery" recipe, automatically set `elasticsearch.skip_restart_on_update`
to true.

Closes #149
Renamed attribute `elasticsearch.skip_restart_on_update` to `elasticsearch.skip_restart`

Related: #149