fetch2/__init__.py: Add connection_cache param in Fetch __init__.
In order to pass connection cache object to checkstatus method.
[YOCTO #7796]
(Bitbake rev: 9fa6407e6cefe66c77467419a8040d6957a6bb01)
Signed-off-by: Aníbal Limón <anibal.limon@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>