Re-enable ManageFirewall by default.

Re-enable ManageFirewall by default.

This default setting got lots in the composable roles/services patches.

Re-enable the ManageFirewall setting by default per what we did in
git commit 73c76b867ddc8a23a30b9a3cac4031189d4178c6.

We also fix a typo in neutron-api.yaml so that the firewall rules
matches to service_name. (otherwise it won't get loaded).

Also, drops the environments/manage-firewall.yaml which is
no longer needed if we enable firewall management by default.

Change-Id: Ie198e4efd190131d0722085b10ef77da9005bc1b
Closes-bug: 1629934