Make 'option to let rrdcached recursively create directories' working.

before: 

Escape character is '^]'.
create aaa/sta_3.rrd -b 1383013773 -s 300 DS:rxrate:GAUGE:600:U:U DS:txrate:GAUGE:600:U:U RRA:AVERAGE:0.5:1:2016 RRA:AVERAGE:0.5:6:1488 RRA:AVERAGE:0.5:24:2160 RRA:AVERAGE:0.5:288:797
-1 RRD Error: creating '/var/lib/rrdcached/db/aaa/sta_3.rrd': No such file or directory
QUIT
Connection closed by foreign host.

after:
Escape character is '^]'.
create aaa/sta_3.rrd -b 1383013773 -s 300 DS:rxrate:GAUGE:600:U:U DS:txrate:GAUGE:600:U:U RRA:AVERAGE:0.5:1:2016 RRA:AVERAGE:0.5:6:1488 RRA:AVERAGE:0.5:24:2160 RRA:AVERAGE:0.5:288:797
0 RRD created OK