Deprecate two security_group-related methods from conductor

The security_group_get_by_instance() and
security_group_rule_get_by_security_group methods are no longer needed
so this patch deprecates them here.

Related to blueprint compute-manager-objects

Change-Id: I43d01fc35b7e0989e96d053e980ebbf020264e37
Merge "Deprecate two security_group-related methods from conductor"