Execute router commands with admin client

The API calls that change the router external gateway info "enable_snat"
flag are, by default, allowed only for admin users. That fix is proposed
to the Neutron API definitions in [1].

[1]https://review.opendev.org/c/openstack/neutron-lib/+/941631

Related-Bug: #2098109
Change-Id: I6c19692fefb09c15423aa58756fb001615ce1ce4
3 files changed