[PATCH] bonding: get slave name from actual slave instead of param list

Take the primary slave name shown in /proc from the actual slave dev
instead of from the command-line parameter, which won't be present
if the bond is created via sysfs.

Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>