net: sched: cleanup qdisc_run and __qdisc_run semantics

Currently __qdisc_run calls qdisc_run_end() but does not call
qdisc_run_begin(). This makes it hard to track pairs of
qdisc_run_{begin,end} across function calls.

To simplify reading these code paths this patch moves begin/end calls
into qdisc_run().

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>