ifupdown2 loses interfaces on second down of swp port

ifupdown2 loses interfaces on second down of swp port

Testing Done: tested bridge and bonds with interfaces with configs

Both bridge and mstpctl modules set priv_flags on interfaces
that have configs (like link-speed) even when used as bridge-ports.
And this collision causes statemanager.ifaceobj_sync() to never get called
because ifaceobj.priv_flags is 1 (we return immediately):
The fix was to create a new iface module_flags array to carry module info.
(cherry picked from commit 56924fef20984fd959939bf7f17c3dd6fd6b137a)
(cherry picked from commit 28d96f7643e2885b1f9c17ad9324a6dbb1b0f8c7)