add shared attribute in creating public network

[Ruijing]

This bug is created to enhance for shared attribute in creating network.

1. easy to create vm in public network.

2. inconsistent attribute

currently, shared attribute is set if creating provider network in lib/neutron as:

NET_ID=$(neutron net-create $PHYSICAL_NETWORK --tenant_id $TENANT_ID --provider:network_type $PROVIDER_NETWORK_TYPE --provider:physical_network "$PHYSICAL_NETWORK" ${SEGMENTATION_ID:+--provider:segmentation_id $SEGMENTATION_ID} --shared | grep ' id ' | get_field 2)

however, shared attribute is not set as:

      if [ "$Q_USE_PROVIDERNET_FOR_PUBLIC" = "True" ]; then
            EXT_NET_ID=$(neutron net-create "$PUBLIC_NETWORK_NAME" -- --router:external=True --provider:network_type=flat --provider:physical_network=${PUBLIC_PHYSICAL_NETWORK} | grep ' id ' | get_field 2)
        else
            EXT_NET_ID=$(neutron net-create "$PUBLIC_NETWORK_NAME" -- --router:external=True | grep ' id ' | get_field 2)
        fi

[Sean Dague (sdague)]

This devstack bug was last updated over 180 days ago, as devstack
is a fast moving project and we'd like to get the tracker down to
currently actionable bugs, this is getting marked as Invalid. If the
issue still exists, please feel free to reopen it.