bonding: do not activate slave twice

bonding: do not activate slave twice

The current code for detecting link during slave addition can cause a
slave interface to be activated twice -- once during slave_configure()
and again at the end of __eth_bond_slave_add_lock_free().  This will
either cause the active slave count to be incorrect or will cause the
802.3ad activation function to panic.  Ensure that the interface is not
activated more than once.

Fixes: 46fb43683679 ("bond: add mode 4")

Signed-off-by: Eric Kinzie <ekinzie@brocade.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Declan Doherty <declan.doherty@intel.com>