Add "apiurl" attribute to the Serviceinfo class

Follow-up commit for 8c45eb64ade699ce3d8717f460b3064ca3ab3a58 (just to
make sure that the "apiurl" attribute is always part of the Serviceinfo
class...)

osc/core.py

@@ -258,6 +258,7 @@ class Serviceinfo:
     def __init__(self):
         """creates an empty serviceinfo instance"""
         self.services = []
+        self.apiurl   = None
         self.project  = None
         self.package  = None