#345 borders out of nowhere when own_window_type dock or panel

[Anonymous]

In conky 1.8.1 compiled:
X11:
* Xdamage extension
* XDBE (double buffer extension)
* Xft
* ARGB visual

Music detection:
* MPD
* MOC

General:
* math
* hddtemp
* portmon
* Curl
* RSS
* wireless
* support for IBM/Lenovo notebooks
* config-output
* Imlib2
* apcupsd
* iostats
* ncurses

with openbox 3.4.11.2 and PCManFM 0.9.8 when you set own_window_type to dock or panel 1px border appears, even if border_width is 0