iw: hanging when doing station or mpath dump

["Andrey Yurovsky" <andrey@cozybit.com>]

We noticed that iw hangs after running "station dump" or "mpath dump"
commands.  The expected output is displayed before the hang.  For
example:

# iw dev mesh station dump

...will display stations (if any) and then hang until iw is killed.
According to strace, iw is waiting on the netlink socket like this:

recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0,
groups=00000000},
msg_iov(1)=[{"\24\0\0\0\3\0\2\0C\256\2I\27\20\0\0\0\0\0\0\0\0\0\0\0\0"...,
4096}], msg_controllen=0, msg_flags=0}, 0) = 20
recvmsg(3,

...which never returns.  This seems to be a somewhat recent regression
but we haven't had a chance to look more closely into it so I'm
mentioning it here in case someone has an idea of what could have gone
wrong.  Thanks,

  -Andrey