iplink: bond: print lacp actor/partner oper states as strings

iplink: bond: print lacp actor/partner oper states as strings

The 802.3ad/LACP actor/partner operating states are only printed as
numbers, e.g,

ad_actor_oper_port_state 15

Add an additional output in ip link show that prints a string describing
the individual 3ad bit meanings in the following way:

ad_actor_oper_port_state_str <active,short_timeout,aggregating,in_sync>

JSON output is also supported, the field becomes a json array:

"ad_actor_oper_port_state_str":
	["active","short_timeout","aggregating","in_sync"]

Signed-off-by: Andy Roulin <aroulin@cumulusnetworks.com>
Signed-off-by: David Ahern <dsahern@gmail.com>