netlink: Unset cb_running when terminating dump on release

netlink: Unset cb_running when terminating dump on release

When we terminated the dump, the callback isn't running, so cb_running
should be set to false to be logically consistent.

cb_running signifies whether a dump is ongoing. It is set to true in
cb->start(), and is checked in netlink_dump() to be true initially.
After the dump, it is set to false in the same function.

This is just a cleanup, no path should access this field on a closed
socket.

Signed-off-by: Siddh Raman Pant <siddh.raman.pant@oracle.com>
Link: https://patch.msgid.link/aff028e3eb2b768b9895fa6349fa1981ae22f098.camel@oracle.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>