MaxFailPercentage: default to 0

Switch the default MaxFailPercentage to 0, to match with the traditional
default.

We're currently working on making MaxFailPercentage working in the
TripleO playbooks (it doesn't work today); so this patch just fix the
default value, 15% was never applied in reality and we don't want to set
any default for backward compatibility. It'll be up to the deployers to
pick their number.

Change-Id: Ifea95c933e7a7d378ddf42050abda790e8631236
(cherry picked from commit 3c8f4a5afd)

overcloud.j2.yaml

@@ -219,10 +219,8 @@ parameters:
   {{role.name}}AnyErrorsFatal:
     default: yes
     type: string
-  {#- We generally won't want any failures on HA Controller roles, 15% will cause any 1 node to fail the deploy, #}
-  {#- for a 3 or 5 node Role, making it a fairly safe default. #}
   {{role.name}}MaxFailPercentage:
-    default: 15
+    default: 0
     type: number
   {{role.name}}Count:
     description: Number of {{role.name}} nodes to deploy