This commit fixes a small oversight in the ostestr --pdb/--no-discover
path. When we go to load the results from the run the command used to
load the results was still using testrepository, which is not used
anywhere else in ostestr at this point.(and is not in requirements.txt
anymore) This commit fixes this and switches it to use stestr instead.
That also exposed another bug in that code path where it was assuming
a repository was created before ostestr was run which is fixed as part
of this commit.
Change-Id: Icb3492ab0f08248a33f711807b150b4a9748fda6
2b3e2e88f7