ifupdown2 loses interfaces on second down of swp port

ifupdown2 loses interfaces on second down of swp port

Ticket: CM-5693
Reviewed By: roopa
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.