cooker: stop loading the cache for -b

cooker: stop loading the cache for -b

Previously, the cache was actually being loaded from disk twice whenever using
-b or -e -b.  This also moves the bb_cache instance into the CookerParser, as
it's not needed by the cooker itself at all.

(Bitbake rev: dd0ec2f7b18e2a9ab06c499b775670516bd06ac8)

Signed-off-by: Chris Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>