mime.bbclass: Add --disable-update-mimedb to EXTRA_OECONF

keep recipes from building files not intended to pack and causing QA warnings [1]

[1] http://lists.linuxtogo.org/pipermail/openembedded-devel/2011-November/035954.html



Signed-off-by: Andreas Müller <schnitzeltony@gmx.de>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>