poky-sanity.bbclass: update conf/templateconf.cfg for existing installations

poky-sanity.bbclass: update conf/templateconf.cfg for existing installations

Updates of existing installations for the meta-yocto to meta-poky transition will
update the bblayers.conf file, but not the templateconf.cfg file. This
patch updates the template file to point to meta-poky/conf, if necessary.

Fixes [YOCTO #9278]

(From meta-yocto rev: e560e9b157fd53cccbe73659b44777715660f0b2)

Signed-off-by: Bill Randle <william.c.randle@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>