netcreate_nova_boot_fip_ping was never using floatingip to
ping as we always call boot_server_with_fip(use_floating_ip=None)
Neutron policy doenst allow users to create router with
external_gateway_info. So we use admin client but still
create router using user tenant id.
Change-Id: I03895c835f5e05daed95bc15f1d6e05acd1c0110
f752b4d463