Use number for KeystoneCronTokenFlushMaxDelay instead of string

Using a string results in an erroneous check in puppet-keystone, which
sets up a zero where it shouldn't. So we change it to number to avoid
that. Note that there will also be a puppet-keystone fix for this.
Changing the value here assures that deployers only give valid values to
this parameter.

Change-Id: I00823e23358df91ce54f421c12636f05d4196e15
Closes-Bug: #1708584

puppet/services/keystone.yaml

@@ -178,10 +178,10 @@ parameters:
         Cron to purge expired tokens - Week Day
     default: '*'
   KeystoneCronTokenFlushMaxDelay:
-    type: string
+    type: number
     description: >
         Cron to purge expired tokens - Max Delay
-    default: '0'
+    default: 0
   KeystoneCronTokenFlushDestination:
     type: string
     description: >