net_sched: introduce qdisc_replace() helper

net_sched: introduce qdisc_replace() helper

Orabug: 25308080

[ Upstream commit 86a7996cc8a078793670d82ed97d5a99bb4e8496 ]

Remove nearly duplicated code and prepare for the following patch.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 11316d7eef2230000bb4fa3d4b9056690fda3ef2)
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>