Adjust net check and docs

* Explain a netcheck in the tshoot docs
* Align postinstall tasks with the skip_dnsmasq ansible var from Kargo

Change-Id: If90ebb26fe768567779ef930819b80038a2f6204
Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

doc/source/troubleshooting.rst

@@ -21,3 +21,20 @@ libvirt and NAT networks. More details can be found in this
 
 Then reporting issues, please also make sure to include details on the host
 OS type and its kernel version.
+
+Network check
+=============
+
+While a net check is a part of deployment process, you can run it manually
+from the admin node as well:
+
+.. code:: sh
+
+      export ws=~/workspace/
+      /usr/bin/ansible-playbook -e ansible_ssh_pass=vagrant -u vagrant -b \
+      --become-user=root -i ~/${ws}inventory/inventory.cfg \
+      -e @${ws}kargo/inventory/group_vars/all.yml \
+      -e @${ws}inventory/kargo_default_common.yaml \
+      -e @${ws}inventory/kargo_default_ubuntu.yaml \
+      -e @${ws}inventory/custom.yaml \
+      ${ws}utils/kargo/postinstall.yml -v --tags postinstall

utils/kargo/roles/postinstall/tasks/main.yml

@@ -1,10 +1,15 @@
 ---
+- name: pick dnsmasq cluster IP
+  set_fact:
+    dnsmasq_server: >-
+      {%- if skip_dnsmasq|bool -%}{{ skydns_server }}{%- else -%}{{ dns_server }}{%- endif -%}
+
 - name: Wait for kubedns to be ready
-  shell: "nslookup kubernetes.default.svc.{{ cluster_name }} {{ dns_server }}"
+  shell: "nslookup kubernetes.default.svc.{{ dns_domain }} {{ dnsmasq_server }}"
   register: kubernetes_resolvable
   until: kubernetes_resolvable.rc == 0
   delay: 5
-  retries: 20
+  retries: 5
   changed_when: false
 
 - name: Copy network test script
@@ -19,7 +24,7 @@
   shell: "bash {{ bin_dir }}/test_networking.sh"
   environment:
     KUBEDNS_IP: "{{ skydns_server }}"
-    DNSMASQ_IP: "{{ dns_server }}"
+    DNSMASQ_IP: "{{ dnsmasq_server }}"
     ADMIN_USER: "{{ ansible_user }}"
     ADMIN_IP: "{{ hostvars[groups['kube-master'][0]]['ip'] | default(hostvars[groups['kube-master'][0]]['ansible_default_ipv4']['address']) }}"
     SLAVE_IPS: "{{ ip }}"