UPDATE 12/14/2015
Final tested draft is here :-
AIO RDO Liberty && Two external networks VLAN provider setup
No switching to "enable_isolated_metadata=True"
END UPDATE
UPDATE 12/12/2015

Be aware of switching to enable_isolated_metadata = True

as well as

neutron subnet-update --host-route destination=169.254.169.254/32,nexthop=10.120.10.151 vlan10
neutron subnet-update --host-route destination=169.254.169.254/32,nexthop=10.120.54.151 vlan54

are important for vlan external network provider
END UPDATE

Take a look at this post https://visibilityspots.org/vlan-flat...
Follow him with vlan external network provider , creating via external networks provider vlan10 ( segmentation_id=10), vlan54 ( segmentation_id=54) with corresponding subnets

# neutron net-create vlan10 --shared --provider:network_type vlan --provider:segmentation_id 10 --provider:physical_network vlan10 --router:external
# neutron subnet-create --name vlan10 --gateway 10.120.10.1 --allocation-pool start=10.120.10.150,end=10.120.10.200 vlan10 10.120.10.1/24

# neutron net-create vlan54 --shared --provider:network_type vlan --provider:segmentation_id 54 --provider:physical_network vlan54 --router:external
#neutron subnet-create --name vlan54 --gateway 10.120.54.1 --allocation-pool start=10.120.54.150,end=10.120.54.200 vlan54 10.120.10.1/24
*************************
openvswitch_agent.ini 
*************************
bridge_mappings vlan10:br-eth0,vlan54:br-eth1
********************
 ml2_conf.ini
********************
network_vlan_ranges = vlan10:10:10, vlan54:54:54

Persistent ifcfg-* supporting this external networks with tags 10, 54
To keep your networking up and running after a reboot you should configure you bridges natively on the all-in-one instance:

X=0,1
/etc/sysconfig/network-scripts/ifcfg-eth(X)

    DEVICE="eth(X)"
    ONBOOT=yes
    OVS_BRIDGE=br-eth(X)
    TYPE=OVSPort
    DEVICETYPE="ovs"

    /etc/sysconfig/network-scripts/ifcfg-br-eth(X)

    DEVICE=br-eth(X)
    BOOTPROTO=none
    ONBOOT=yes
    TYPE=OVSBridge
    DEVICETYPE="ovs"

Then create

/etc/sysconfig/network-scripts/ifcfg-br-eth0.10
/etc/sysconfig/network-scripts/ifcfg-br-eth1.54

Having

******************
ifcfg-br-eth0.10
******************
BOOTPROTO="none"
DEVICE="br-eth0.10"
ONBOOT="yes"
IPADDR="10.120.10.10"
PREFIX="24"
GATEWAY="10.120.10.1"
VLAN=yes
NOZEROCONF=yes
USERCTL=no
******************
ifcfg-br-eth1.54
******************
BOOTPROTO="none"
DEVICE="br-eth1.54"
ONBOOT="yes"
IPADDR="10.120.54.54"
PREFIX="24"
GATEWAY="10.120.54.1"
VLAN=yes
NOZEROCONF=yes
USERCTL=no

Supporting 2 vlan external networks with one l3-agent is not a problem
http://funcptr.net/2014/09/29/neutron...