tc: improve the qdisc show command

tc: improve the qdisc show command

Before can be possible show only all qeueue disciplines on an interface.
There wasn't a way to get the qdisc info by handle or parent, only full
dump of the disciplines with a following grep/sed usage.

Now new and old options work as expected to filter a qdisc by handle or
parent.

Full syntax of the qdisc show command:

tc qdisc { show | list } [ dev STRING ] [ QDISC_ID ] [ invisible ]
  QDISC_ID := { root | ingress | handle QHANDLE | parent CLASSID }

This change doesn't require any changes in the kernel.

Signed-off-by: Anton Danilov <littlesmilingcloud@gmail.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>