Replace over_provisioning_mapping with Stagiaire call

Summary:
> This diff should ONLY be shipped after monitoring Stagiaire Scuba for a few more days

```

Differential Revision: D57170934

fbshipit-source-id: 1c91d411dac4c3632065fe390446daea58d6b207

cookbooks/fb_storage/README.md

@@ -17,7 +17,6 @@ Attributes
 * node['fb_storage']['tuning']['queue_depth']
 * node['fb_storage']['tuning']['discard_max_bytes']
 * node['fb_storage']['tuning']['over_provisioning']
-* node['fb_storage']['tuning']['over_provisioning_mapping']
 * node['fb_storage']['tuning']['max_sectors_kb']
 * node['fb_storage']['fstab_use_labels']
 * node['fb_storage']['manage_packages']
@@ -326,9 +325,8 @@ storage controlled by this API: `queue_depth`, `scheduler`,
 Note: `max_sectors_kb` sets the maximum IO sizes to the minimum of the device's
 `max_hw_sectors_kb` and the one provided.
 
-The `over_provisioning` and `over_provisioning_mapping` attributes are provided
-for storage handlers to manage over provisioning, but are currently not used
-by `fb_storage` itself.
+The `over_provisioning` attribute is provided for storage handlers to manage
+over provisioning, but are currently not used by `fb_storage` itself.
 
 ### Software Raid
 

cookbooks/fb_storage/attributes/default.rb

@@ -35,7 +35,6 @@
     'scheduler' => nil,
     'queue_depth' => nil,
     'over_provisioning' => 'low',
-    'over_provisioning_mapping' => {},
     'max_sectors_kb' => nil,
   },
   'format_options' => nil,