orangefs: Fix sb refcount leak when allocate sb info failed.

The reference counting issue happens in one exception handling
path of orangefs_mount(). When failing to allocate sb info, the
function forgets to decrease the refcount of sb increased by
sget(), causing a refcount leak.

Fix this issue by jumping to the label "free_sb_and_op" instead
of "free_op"

Signed-off-by: Chenyuan Mi <cymi20@fudan.edu.cn>
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>