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/roles/install-configure-bifrost/tasks/cleanup-bifrost.yml b/playbooks/roles/install-configure-bifrost/tasks/cleanup-bifrost.yml
index 4a51eb8..1743911 100644
--- a/playbooks/roles/install-configure-bifrost/tasks/cleanup-bifrost.yml
+++ b/playbooks/roles/install-configure-bifrost/tasks/cleanup-bifrost.yml
@@ -18,8 +18,8 @@
 # ============LICENSE_END=========================================================
 - name: Stop existing libvirt dnsmasq processes
   command: killall -w dnsmasq
-  ignore_errors: yes
-  become: yes
+  ignore_errors: true
+  become: true
   changed_when: false
 
 - name: Remove existing files and directories
@@ -31,6 +31,6 @@
     - "/etc/dnsmasq.d/bifrost.dhcp-hosts.d/"
     - "/var/lib/misc/dnsmasq.leases"
     - "{{ ansible_env.HOME }}/.config/openstack"
-  become: yes
+  become: true
 
 # vim: set ts=2 sw=2 expandtab: