Fix to make the error message readable for #872

[mocchira]

• Before

  [E]     storage_0@127.0.0.1     2017-11-02 15:23:33.294359 +0900        1509603813      leo_storage_app:launch_object_storage    292     CRASH REPORT Process <0.49.0> with 0 neighbours exited with reason: no mat
  ch of right hand value {error,{{'EXIT',invalid_launch},{child,undefined,leo_object_storage_sup,{leo_object_storage_sup,start_link,[[{8,"/mnt/leofs"}],leo_storage_msg_collector]},permanent,2000,supervisor,[leo_ob
  ject_storage_sup]}}} in leo_storage_app:launch_object_storage/1 line 292 in application_master:init/4 line 134
  [E]     storage_0@127.0.0.1     2017-11-02 15:23:38.55047 +0900 1509603818      null:null       0       CRASH REPORT Process <0.113.0> with 0 neighbours exited with reason: enoent in gen_server:init_it/6 line 34
  9

• After

  [E]     storage_0@127.0.0.1     2017-11-02 15:45:14.167734 +0900        1509605114      leo_storage_app:launch_object_storage   292     CRASH REPORT Process <0.50.0> with 0 neighbours exited with reason: no matc
  h of right hand value {error,{{'EXIT',invalid_launch},{child,undefined,leo_object_storage_sup,{leo_object_storage_sup,start_link,[[{8,"/mnt/leofs/avs"}],leo_storage_msg_collector]},permanent,2000,supervisor,[leo
  _object_storage_sup]}}} in leo_storage_app:launch_object_storage/1 line 292 in application_master:init/4 line 134
  [E]     storage_0@127.0.0.1     2017-11-02 15:45:19.463534 +0900        1509605119      null:null       0       {module,"leo_file"},{function,"ensure_dir/1"},{line,298},{body,{file,"/mnt/leofs/avs/metadata"},{re
  sult,eacces}}

Related PR

• https://github.com/leo-project/leo_object_storage/pull/15

[yosukehara]

Link: leo-project/leofs/issues/872