LU-12431 clio: remove default csi_end_io handler

LU-12431 clio: remove default csi_end_io handler

Since the csi_end_io is empty remove it.
Provide an initialize that supports a custom end_io handler.

Cray-bug-id: LUS-7330
Signed-off-by: Shaun Tancheff <stancheff@cray.com>
Change-Id: If62c2536772136bfafc6e99ad1dbd9b466735201
Reviewed-on: https://review.whamcloud.com/35400
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>