Use group_regex to serialize scrubber tests

Instead of doing two separate test runs, use the group_regex option to
stestr to group tests that cannot be run in parallel into the same
worker.

Change-Id: I3d69d5c72d69484f4e1c9c0b11122d0cf3703d60
Related-Bug: #1768077

.stestr.conf

@@ -1,3 +1,4 @@
 [DEFAULT]
 test_path=${TEST_PATH:-./glance/tests/unit}
 top_dir=./
+group_regex=(glance\.tests\.functional\.serial\.[^.]+\.)

serial-functests.txt

@@ -1 +0,0 @@
-^glance\.tests\.functional\.serial\.*

tools/generate-blacklist.sh

@@ -1,9 +0,0 @@
-#!/bin/bash -xe
-
-TOX_INI_DIR="$1"
-TOX_TMP_DIR="$2"
-
-cat "${TOX_INI_DIR}/serial-functests.txt" \
-    "${TOX_INI_DIR}/broken-functional-py35-ssl-tests.txt" > \
-    "${TOX_TMP_DIR}/func-py35-blacklist.txt"
-

tox.ini

@@ -40,8 +40,7 @@ setenv =
   TEST_PATH = ./glance/tests/functional
 ignore_errors = True
 commands =
-  stestr run --blacklist-file ./serial-functests.txt {posargs}
-  stestr run --serial --combine --whitelist-file ./serial-functests.txt {posargs}
+  stestr run {posargs}
 
 [testenv:functional-py35]
 basepython = python3.5
@@ -51,11 +50,7 @@ ignore_errors = True
 whitelist_externals =
   bash
 commands =
-  # NOTE(rosmaita): calling this script is a complete hack, everything
-  # is hard-coded.
-  bash tools/generate-blacklist.sh {toxinidir} {envtmpdir}
-  stestr run --blacklist-file {envtmpdir}/func-py35-blacklist.txt {posargs}
-  stestr run --serial --combine --whitelist-file ./serial-functests.txt {posargs}
+  stestr run --blacklist-file ./broken-functional-py35-ssl-tests.txt {posargs}
 
 [testenv:broken-py35-ssl-tests]
 # NOTE(rosmaita): these tests were being skipped due to bug #1482633, but we