BGP-FS extended communities are not serialized

steps to reproduce:
-run ODL with configured app-peer and peer
-add a new FS route (including FS extended community)
-the FS route is advertised a connected peer
-observe output message byte stream
-the extended community value is missing, only type and subtype included

Example: 8007 == type=128, subtype=7
ffffffffffffffffffffffffffffffff006e02000000574001010040020040050400000064800a00800e390001850000330120c0a8000102200a00000103810604815005121f90d41f98069204000781000881000981200a120190d401f40b81140c8104c010028007c010028007