Improve the setup scripts to support multi-nics

This commit improves the setup scripts to support multi-nics:
1. update kube_master playbook to read kubeadm init parameter from
   environment variable
2. add one note into development-environment-devstack doc

Change-Id: Ie5fa11cc0d0b1a4cf5bd388b80a12a3f00295788

doc/source/contributor/development-environment-devstack.rst

@@ -71,6 +71,18 @@ configuration:
 
 .. end
 
+.. note::
+
+   For multiple network cards, you need to update the Kubernetes apiserver's advertise address
+   to the address on the interface which is used to get to the default gateway by adding one
+   environment variable.
+
+   .. code-block:: console
+
+       export EXTRA_KUBEADM_INIT_OPTS="--apiserver-advertise-address <default-host-ip>"
+
+   .. end
+
 Running devstack
 ----------------
 
@@ -109,4 +121,4 @@ set up during devstack installation.
 
 Qinling devstack script uses `kubeadm <https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/>`_
 for Kubernetes installation, refer to ``tools/gate/kubeadm/setup_gate.sh`` for
-more detailed information about Qinling devstack installation.
+more detailed information about Qinling devstack installation.

tools/gate/kubeadm/playbook/roles/kube_master/tasks/main.yml

@@ -15,7 +15,9 @@
   ignore_errors: True
 
 - name: Init master
-  shell: kubeadm init --pod-network-cidr=192.168.0.0/16 --kubernetes-version=1.9.3
+  vars:
+    extra_opts: "{{ lookup('env', 'EXTRA_KUBEADM_INIT_OPTS') }}"
+  shell: kubeadm init --pod-network-cidr=192.168.0.0/16 --kubernetes-version=1.9.3 {{ extra_opts }}
   register: kubeadm_init
 
 - fail: