Before returning config instances from Scheduler._allocate_config(), call the

Before returning config instances from Scheduler._allocate_config(), call the
config.reset() method to make sure all settings from the previous package get
flushed out (such as PORTAGE_LOG_FILE). This fixes a case where
PORTAGE_LOG_FILE leaked from the previous package to the clean phase of the
next one, resulting in an IOError due to the path being invalid and the parent
directory being nonexistent.

svn path=/main/trunk/; revision=11655