updated scylla version and removed simplestrategy

[guy9]

@tzach please review

[tarzanek]

(so ideally network strategy change should be in separate commit, so you have isolated patch) why going for exact scylla version @guy9 ? I'd think we can just leave latest and if something will break people will report, it's probably better than people using old Scyllas or us changing version every few months, isn't it? @tzach ?

[tzach]

LGTM