Replace deprecated assertDictContainsSubset
Replace deprecated assertDictContainsSubset

The method is deprecated since Python 3.2[1] and shows the following
DeprecationWarning.

/usr/lib/python3.9/unittest/case.py:1134: DeprecationWarning:
assertDictContainsSubset is deprecated
  warnings.warn('assertDictContainsSubset is deprecated',

[1] https://docs.python.org/3/whatsnew/3.2.html#unittest

Change-Id: I8cc3b29ff5e1635143761bf4c072d57cd78d3138

openstack/python-ironic-inspector-client