Fix yamllint issues and make it blocker

All yamllint issues in yaml files have been fixed except line-length rule
which is excluded. tox.ini is updated in order not to ignore yamllint issues
so if yamllint fails, the change will get verified-1 and will be blocked from
merging. yamllint configuration file, .yamllint, is also created to configure
what is enforced.

As a summary, most frequently occurring issues that are fixed are below.
- truthy value: must be true/false and not yes/no
- indentation: blocks are incorrectly indented mostly
- braces: extra spaces after opening and before closing curly braces are not good
- colons: extra spaces after colons - should be single
- missing document start
- comments: there should be a space after hash

Change-Id: I0d1341f2639585228b1ae8fd6ee073e5cae53604
diff --git a/playbooks/pre-deployment.yml b/playbooks/pre-deployment.yml
index b307cee..55a9b0a 100644
--- a/playbooks/pre-deployment.yml
+++ b/playbooks/pre-deployment.yml
@@ -20,8 +20,8 @@
 # check if any pre-deployment task defined for the scenario
 - hosts: localhost
   connection: local
-  gather_facts: no
-  become: no
+  gather_facts: false
+  become: false
 
   tasks:
     - name: Check if any pre-deployment task defined for '{{ deploy_scenario }}' scenario
@@ -31,8 +31,8 @@
 
 # run the scenario pre-deployment tasks before running the deployment itself
 - hosts: all
-  gather_facts: yes
-  become: yes
+  gather_facts: true
+  become: true
 
   tasks:
     - name: Execute pre-deployment tasks of '{{ deploy_scenario }}' scenario