Problem: Incorrect parse when arbitrary keys present.

[zerthimon]

When keys are set with record_transformer filter, the plugin fails to parse correctly (all values go into sql key):

Config to reproduce:

<source>
  @type tail
  path /fluentd/mysql/mysql-slow.log
  format /^(?<message>.+)$/
  tag mysqld.slow
</source>

<filter mysqld.slow>
  @type record_transformer
  <record>
    docker_host docker.host.name
  </record>
  <record>
    env env_name
  </record>
  <record>
    region region_name
  </record>
  <record>
    geo_region geo_region_name
  </record>
</filter>

<match mysqld.slow>
  @type mysqlslowquerylog
  add_tag_prefix concatenated.
</match>

<match concatenated.**>
  @type file
  @id output1
  path /fluentd/log/data.*.log
  flush_interval 5s
  append true
  time_slice_format %Y%m%d
  time_slice_wait 10m
  time_format %Y%m%dT%H%M%S%z
</match>

Input:

# Time: 130107 11:36:21
# User@Host: root[root] @ localhost []
# Query_time: 0.000378  Lock_time: 0.000111 Rows_sent: 7  Rows_examined: 7
SET timestamp=1357526181;
select * from user;
# Time: 130107 11:38:47
# User@Host: root[root] @ localhost []
# Query_time: 0.002142  Lock_time: 0.000166 Rows_sent: 142  Rows_examined: 142
use information_schema;
SET timestamp=1357526327;
select * from INNODB_BUFFER_PAGE_LRU;

output:

2013-01-07T11:36:21+00:00	concatenated.mysqld.slow	{"user":null,"host":null,"query_time":0.0,"lock_time":0.0,"rows_sent":0,"rows_examined":0,"sql":"region_name geo_region_name # User@Host: root[root] @ localhost [] docker.host.name env_name region_name geo_region_name # Query_time: 0.000378  Lock_time: 0.000111 Rows_sent: 7  Rows_examined: 7 docker.host.name env_name region_name geo_region_name SET timestamp=1357526181; docker.host.name env_name region_name geo_region_name select * from user;"}
2013-01-07T11:38:47+00:00	concatenated.mysqld.slow	{"user":null,"host":null,"query_time":0.0,"lock_time":0.0,"rows_sent":0,"rows_examined":0,"sql":"region_name geo_region_name # User@Host: root[root] @ localhost [] docker.host.name env_name region_name geo_region_name # Query_time: 0.002142  Lock_time: 0.000166 Rows_sent: 142  Rows_examined: 142 docker.host.name env_name region_name geo_region_name use information_schema; docker.host.name env_name region_name geo_region_name SET timestamp=1357526327; docker.host.name env_name region_name geo_region_name select * from INNODB_BUFFER_PAGE_LRU;"}