bridging: update the ifcfg files generated for bridge slaves

Update the ifcfg files generated for bridge slaves so they reference
the bridge they are part of.  Related to early patch submitted as a
fix for Bug #1123552.

Bug #1123552 https://bugzilla.redhat.com/show_bug.cgi?id=1123552

modules.d/45ifcfg/write-ifcfg.sh

@@ -234,8 +234,7 @@ for netup in /tmp/net.*.did-setup ; do
                 echo "ONBOOT=yes"
                 echo "NETBOOT=yes"
                 echo "HWADDR=\"$(cat /sys/class/net/$slave/address)\""
-                echo "SLAVE=yes"
+                echo "BRIDGE=\"$bridgename\""
-                echo "MASTER=\"$bridgename\""
                 echo "NAME=\"$slave\""
                 echo "UUID=\"$(cat /proc/sys/kernel/random/uuid)\""
             } >> /tmp/ifcfg/ifcfg-$slave