Add resource capacity property

Resource(VCPU, memory and disk) capacity need to be calculated
through formula: capacity = (total-reserved)*ratio.

Partially Implements: blueprint improve-compute-data-model

Change-Id: I15ca66dd2c3a21c5acfebf6f04fa6601aff7918f

watcher/decision_engine/model/element/node.py

@@ -56,6 +56,18 @@ class ComputeNode(compute_resource.ComputeResource):
     def accept(self, visitor):
         raise NotImplementedError()
 
+    @property
+    def memory_mb_capacity(self):
+        return (self.memory-self.memory_mb_reserved)*self.memory_ratio
+
+    @property
+    def disk_gb_capacity(self):
+        return (self.disk-self.disk_gb_reserved)*self.disk_ratio
+
+    @property
+    def vcpus_capacity(self):
+        return (self.vcpus-self.vcpu_reserved)*self.vcpu_ratio
+
     @property
     def memory_mb_free(self):
         total = (self.memory-self.memory_mb_reserved)*self.memory_ratio