ceph-detect-init & ceph-disk: Pin testtools test requirement

ceph-detect-init & ceph-disk: Pin testtools test requirement

When running make-check on python 3.4, the test requirements
installation fails with:

ERROR: testtools requires Python '>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, \
  !=3.3.*, !=3.4.*' but the running Python is 3.4.6

This happens because there is a new testtols release on pypi from Mar
14, 2020. Pinning to an older version fixes this.

This is not needed for Master, Octopus and Nautilus  given that python
3.4 is already EOL[1] before Nautilus got released.

[1] https://www.python.org/downloads/release/python-3410/

Signed-off-by: Thomas Bechtold <tbechtold@suse.com>