net: ipv4: current group_info should be put after using.

net: ipv4: current group_info should be put after using.

Plug a group_info refcount leak in ping_init.
group_info is only needed during initialization and
the code failed to release the reference on exit.
While here move grabbing the reference to a place
where it is actually needed.

Signed-off-by: Chuansheng Liu <[email protected]>
Signed-off-by: Zhang Dongxing <[email protected]>
Signed-off-by: xiaoming wang <[email protected]>
Signed-off-by: David S. Miller <[email protected]>