Fix the issue of unmarshal string into Go struct field StoragePool.capabilities

The MaxOverSubscriptionRatio type should be string because max_over_subscription_ratio returned by cinder is a string, not float.

Change-Id: I9c2100df11aa686a52e7bdabbcf3154638bc6b2c
diff --git a/openstack/blockstorage/extensions/schedulerstats/results.go b/openstack/blockstorage/extensions/schedulerstats/results.go
index 3fade69..c7b3e73 100644
--- a/openstack/blockstorage/extensions/schedulerstats/results.go
+++ b/openstack/blockstorage/extensions/schedulerstats/results.go
@@ -23,7 +23,7 @@
 	LocationInfo             string  `json:"location_info"`
 	QoSSupport               bool    `json:"QoS_support"`
 	ProvisionedCapacityGB    float64 `json:"provisioned_capacity_gb"`
-	MaxOverSubscriptionRatio float64 `json:"max_over_subscription_ratio"`
+	MaxOverSubscriptionRatio string  `json:"max_over_subscription_ratio"`
 	ThinProvisioningSupport  bool    `json:"thin_provisioning_support"`
 	ThickProvisioningSupport bool    `json:"thick_provisioning_support"`
 	TotalVolumes             int64   `json:"total_volumes"`