Fix tox.ini for tox4

Use allowlist_externals instead of whitelist_externals.
Execute shell script with bash.

Change-Id: If34dbe6c8456ade6e37951a70a89bc5d22de3048
(cherry picked from commit 8bee5cc07e)

tox.ini

@@ -1,7 +1,6 @@
 [tox]
 envlist = py3,pep8,pylint
 minversion = 3.1.1
-skipsdist = True
 
 [testenv]
 setenv = VIRTUAL_ENV={envdir}
@@ -14,9 +13,9 @@ install_command =pip install {opts} {packages}
 deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/zed}
        -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-whitelist_externals =
+allowlist_externals =
   find
-  sh
+  bash
 commands =
   find . -type f -name "*.py[c|o]" -delete
   find . -type l -name "*.py[c|o]" -delete
@@ -64,7 +63,7 @@ commands =
 [testenv:pdf-docs]
 envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
-whitelist_externals =
+allowlist_externals =
   make
 commands =
   sphinx-build -W -b latex doc/source doc/build/pdf
@@ -104,7 +103,7 @@ import_exceptions = neutron_dynamic_routing._i18n
 local-check-factory = neutron_lib.hacking.checks.factory
 
 [testenv:genconfig]
-commands = {toxinidir}/tools/generate_config_file_samples.sh
+commands = bash {toxinidir}/tools/generate_config_file_samples.sh
 
 [testenv:genpolicy]
 commands = oslopolicy-sample-generator --config-file=etc/oslo-policy-generator/policy.conf