addons: mstpctl: bridge vlan-unaware: check brport running config before setting...

addons: mstpctl: bridge vlan-unaware: check brport running config before setting attributes

when handling mstpctl attribute on vlan-unaware bridges we don't
check the running configuration of the bridge ports (cache) thus
misconfiguring some attributes on brports.

We first create a traditional bridge with:

auto bridge1
iface bridge1
    bridge-ports swp1 swp2
    bridge-vlan-aware no
We check the setting:

$ mstpctl showportdetail bridge1 swp1 | grep edge
  admin edge port    no                      auto edge port       yes
  oper edge port     yes                     topology change ack  no
We then add the setting for swp1:

auto swp1
iface swp1
    mstpctl-portautoedge no
We then do an ifreload -adv and we see two calls. First
info: executing /sbin/mstpctl setportautoedge bridge1 swp1 no

and then a little later
info: executing /sbin/mstpctl setportautoedge bridge1 swp1 yes

Reviewed-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: Julien Fortin <julien@cumulusnetworks.com>