TestSuite: fix new document ids
TestSuite: fix new document ids

New document IDs are only generated when there is no ID key at all in
the new object's dictionary when passed to utils.db.save() - having a
key set to None results in a null key in the database.  Fix this by
reverting to only adding an ID key when the object already has a valid
ID.

Fixes: 21f1eb56e714 ("Add boot meta-data to TestSuiteDocument")
Signed-off-by: Guillaume Tucker <e7e20b7c30f19d4ca6b81319ef81bf200369d137@collabora.com>

kernelci/kernelci-backend,kernelci/kernelci-backend