Summary:
since we did this live at Flock today, I figured I'd tidy it
up and submit it. This is an 'optional' test, but some people
do run this way so it'd be nice to have it. This adds another
little helper method in anacondatest.pm, for deleting partitions,
which works much like the others added in previous commits.
Test Plan: Schedule a test run, see if the test runs and works.
Reviewers: jskladan, garretraziel
Reviewed By: jskladan, garretraziel
Subscribers: tflink
Differential Revision: https://phab.qadevel.cloud.fedoraproject.org/D503
