lib, vtysh: fix inconsistent interface commands in vtysh

lib, vtysh: fix inconsistent interface commands in vtysh

The definition of the interface commands in vtysh.c were outdated.
Currently, all daemons that call if_cmd_init() will have the "no interface
IFNAME" command and the "[no] description" commands as well, so there's
no need to define exceptions for these commands anymore.

To fix this, make extract.pl parse the if.c file so that vtysh can get the
interface commands from there automatically. Only the "interface IFNAME
[vrf NAME]" must be kept in vtysh.c because it changes the vty node and
thus needs special treatment.

Finally, make pimd and pbrd display interface descriptions on "sh run"
when they are configured.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>