cfg80211: NL80211_ATTR_SOCKET_OWNER support for CMD_CONNECT

Disconnect or deauthenticate when the owning socket is closed if this
flag is supplied to CMD_CONNECT or CMD_ASSOCIATE.  This may be used
to ensure userspace daemon doesn't leave an unmanaged connection behind.

In some situations it would be possible to account for that, to some
degree, in the deamon restart code or in the up/down scripts without
the use of this attribute.  But there will be systems where the daemon
can go away for varying periods without a warning due to local resource
management.

Signed-off-by: Andrew Zaborowski <andrew.zaborowski@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>