When we break a stripe_batch_list we sometimes want to set
STRIPE_HANDLE on the individual stripes, and sometimes not.

So pass a 'handle_flags' arg.  If it is zero, always set STRIPE_HANDLE
(on non-head stripes).  If not zero, only set it if any of the given
flags are present.
Signed-off-by: NeilBrown <neilb@suse.de>