[PATCH] fix bd_claim_by_kobject error handling

This fixes bd_claim_by_kobject to release bdev correctly in case that
bd_claim succeeds but following add_bd_holder fails.

Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>