Allow for url override for Compute

* Adds a config value for the base Compute url

Change-Id: Ifca379796f26dfb8a25810a0b8c323b1fcf86743

cloudcafe/compute/config.py

@@ -38,6 +38,11 @@ class ComputeEndpointConfig(ConfigSectionInterface):
     def compute_endpoint_name(self):
         return self.get("compute_endpoint_name")
 
+    @property
+    def compute_endpoint_url(self):
+        """Optional override of the Compute url"""
+        return self.get("compute_endpoint_url")
+
 
 class ComputeAdminEndpointConfig(ComputeEndpointConfig):