Use - instead of . for physical_resource_name delim.

Avoiding using . means that instance hostnames are unique within the stack
(and within the tenant).

This solves 2 real-world use cases:
- tripleo issue, as described in bug: #1184713
- OpenShift template resorts to setting the hostname to ec2_instance_id

This may have an impact on users who are scripting to assume . delimiting,
however this will only affect newly created stacks after this change is
deployed.

Fixes bug: #1184713

Change-Id: I5a8eb358ea9c52162eb9263b9f9e6dcf750d787b

heat/engine/resource.py

@@ -403,7 +403,7 @@ class Resource(object):
             self.state_set(self.UPDATE_COMPLETE)
 
     def physical_resource_name(self):
-        return '%s.%s' % (self.stack.name, self.name)
+        return '%s-%s' % (self.stack.name, self.name)
 
     def validate(self):
         logger.info('Validating %s' % str(self))

heat/tests/utils.py

@@ -80,4 +80,4 @@ class PhysName(object):
         return not self.__eq__(physical_name)
 
     def __repr__(self):
-        return '%s.%s' % (self.stack_name, self.resource_name)
+        return '%s-%s' % (self.stack_name, self.resource_name)