Fix jobs after tox4 upgrade

Following the recommendations provided in [1], this patch disables the
"skipsdist" flag. Also format passenv values due to cannot contain
whitespace, and add allowlist_externals where necessary because looks
more strictly checked.

[1]https://github.com/tox-dev/tox/issues/2730

Change-Id: Iea8e355cd18c51a00bdbe5225239965cfc1704d7
(cherry picked from commit ef019ed63b)

tox.ini

@@ -1,7 +1,7 @@
 [tox]
 minversion = 3.18.0
 envlist = docs,py38,pep8
-skipsdist = True
+skipsdist = False
 ignore_basepython_conflict = True
 
 [testenv]
@@ -16,8 +16,14 @@ deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/up
        -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 allowlist_externals = bash
-                      sh
-passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY TOX_ENV_SRC_MODULES
+                      {toxinidir}/tools/pip_install_src_modules.sh
+passenv = http_proxy
+          HTTP_PROXY
+          https_proxy
+          HTTPS_PROXY
+          no_proxy
+          NO_PROXY
+          TOX_ENV_SRC_MODULES
 commands =
   {toxinidir}/tools/pip_install_src_modules.sh "{toxinidir}"
   stestr run {posargs}
@@ -29,6 +35,10 @@ commands = flake8
            {toxinidir}/tools/coding-checks.sh --pylint '{posargs}'
            {[testenv:bandit]commands}
            {[testenv:genconfig]commands}
+allowlist_externals =
+    {toxinidir}/tools/check_unit_test_structure.sh
+    {toxinidir}/tools/coding-checks.sh
+    {toxinidir}/tools/generate_config_file_samples.sh
 
 [testenv:venv]
 commands = {posargs}
@@ -124,6 +134,8 @@ paths =./ovn_octavia_provider/hacking
 [testenv:genconfig]
 envdir = {toxworkdir}/shared
 commands = {toxinidir}/tools/generate_config_file_samples.sh
+allowlist_externals =
+    {toxinidir}/tools/generate_config_file_samples.sh
 
 # This environment can be used to quickly validate that all needed system
 # packages required to successfully execute test targets are installed
@@ -138,9 +150,9 @@ commands = bindep test
 [testenv:requirements]
 deps =
   -egit+https://opendev.org/openstack/requirements#egg=openstack-requirements
-allowlist_externals = sh
+allowlist_externals = bash
 commands =
-    sh -c '{envdir}/src/openstack-requirements/playbooks/files/project-requirements-change.py --req {envdir}/src/openstack-requirements --local {toxinidir} master'
+    bash -c '{envdir}/src/openstack-requirements/playbooks/files/project-requirements-change.py --req {envdir}/src/openstack-requirements --local {toxinidir} master'
 
 [testenv:bandit]
 envdir = {toxworkdir}/shared