XenAPI: Generic Fake.get_all_records_where implementation

Tests were incorrectly passing due to bad implementations.

Note that link to xenserver-core blueprint is due to patch following this
change

Implements blueprint xenserver-core

Change-Id: I051877551611e001295403af8369bcc97c8ba0fb
Merge "XenAPI: Generic Fake.get_all_records_where implementation"