LU-1235 osd: delete commit cb entry list first

LU-1235 osd: delete commit cb entry list first

delte commit cb entry list before calling the commit callback
functions.

Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: I183d31e09666626724f5adcbd977670d558ae219
Reviewed-on: http://review.whamcloud.com/2791
Reviewed-by: Mike Pershin <tappro@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: hongchao.zhang <hongchao.zhang@whamcloud.com>
Tested-by: hongchao.zhang <hongchao.zhang@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>