In the case of a single node environment without haproxy, the var
"kolla_internal_vip_adress" in global.yml should be the ip address
of the host. However, the prechecks will fail, because this ip
address is used by the host node and is pingable.

This commit fixes the prechecks of a vip address properly.
When the var "enable_haproxy" is "no", this fix will skip prechecks
for a vip address.

Change-Id: I0b752f179d20f82e3d6331047ee0bd802ab99a4b
Closes-Bug: #1570935