xend: Remove _setSchedParams

xend: Remove _setSchedParams

Currently, xc.sched_credit_domain_set is called twice when domains
are created.

start@XendDomainInfo
  _constructDomain
    xc.sched_credit_domain_set  --- 1st
  _initDomain
    _setSchedParams
      domain_sched_credit_set
        xc.sched_credit_domain_set  --- 2nd

resume@XendDomainInfo
  _constructDomain
    xc.sched_credit_domain_set  --- 1st
  _setSchedParams
    domain_sched_credit_set
      xc.sched_credit_domain_set  --- 2nd

This patch removes _setSchedParams method added by changeset 19955,
because xc.sched_credit_domain_set was added into _constructDomain
method by changeset 20006.

Signed-off-by: Masaki Kanno <kanno.masaki@jp.fujitsu.com>