Add ostestr tox jobs

This commit adds tox jobs to run tempest with ostestr instead of the
pretty_tox*.sh wrappers. ostestr provides essentially the same
functionality except it exposes slightly more rich selection logic
and additional debugging options. However, since the cli isn't
backwards compatible with pretty_tox we can't simply remove the old
tox jobs.

Change-Id: I347438b1d561af7e05fdce895e2e3e51d2b38b0c

tox.ini

@@ -45,6 +45,17 @@ commands =
     find . -type f -name "*.pyc" -delete
     bash tools/pretty_tox.sh '{posargs}'
 
+[testenv:ostestr]
+sitepackages = {[tempestenv]sitepackages}
+# 'all' includes slow tests
+setenv =
+    {[tempestenv]setenv}
+    OS_TEST_TIMEOUT={env:OS_TEST_TIMEOUT:1200}
+deps = {[tempestenv]deps}
+commands =
+    find . -type f -name "*.pyc" -delete
+    ostestr {posargs}
+
 [testenv:all-plugin]
 sitepackages = True
 # 'all' includes slow tests