Changes return ability to use HostMapping.save method,
it was broken.
It fixes two issues:
- HostMapping._save_in_db got unexpected parameter
(self.host instead of self object from the save call).
It's clear.
- "sqlalchemy.orm.exc.DetachedInstanceError: Parent instance
<HostMapping> is not bound to a Session;"
while trying to get the cell_mapping attribute on saved HostMapping
instance.
As HostMapping cannot be without cell_mapping, solution is to load
cell_mapping attribute just after getting it from DB.
To be consistent I used the code from _create_in_db method.
Closes-bug: 1595587
Change-Id: Ia2e427f5bd4ab43d1c273de72ef7bb8c01d8d1af
daad6c26ec