log the missing bucket type name when returning {error, no_type}

[joecaswell]

Adresses #815

Manual test:

% tail -n1 log/console.log
2016-02-29 13:17:51.096 [info] <0.445.0>@riak_kv_entropy_manager:perhaps_log_throttle_change:853 Changing AAE throttle from undefined -> 0 msec/key, based on maximum vnode mailbox size 1 from '[email protected]'

% bin/riak-admin bucket-type list
default (active)
goodtype (active)

% bin/riak attach
Remote Shell: Use "Ctrl-C a" to quit. q() or init:stop() will terminate the riak node.
Eshell V5.10.3  (abort with ^G)

([email protected])1> riak_kv_util:get_index_n({{<<"goodtype">>,<<"bucket">>},<<"key">>}).
{616571003248974668617179538802181898917346541568,4}

([email protected])2> riak_kv_util:get_index_n({{<<"badtype">>,<<"bucket">>},<<"key">>}). 
** exception error: no function clause matching proplists:get_value(n_val,{error,no_type},undefined) (proplists.erl, line 225)
     in function  riak_kv_util:get_index_n/1 (src/riak_kv_util.erl, line 190)

([email protected])3> 
^C%                                                                                                                                                                                                                                                        

% tail -n2 log/console.log     
2016-02-29 13:17:51.096 [info] <0.445.0>@riak_kv_entropy_manager:perhaps_log_throttle_change:853 Changing AAE throttle from undefined -> 0 msec/key, based on maximum vnode mailbox size 1 from '[email protected]'
2016-02-29 13:18:55.144 [error] <0.2626.0>@riak_core_bucket:get_bucket:124 {error,no_type} getting properties of bucket {<<"badtype">>,<<"bucket">>}

[bsparrow435]

+1 ac92614

[bsparrow435]

👍 ac92614

[bsparrow435]

@borshop merge