Update tox.ini to work with tox 4

Tox 4 deprecated whitelist_externals.
Replace whitelist_externals with allowlist_externals
Tox 4 Fail on pass_env/passenv entries containing whitespace.
Updated passenv with comma separated values

Also, we need to temporary turn off coverage job, since it compares
stats of current change with a previous one. It is impossible to collect
stats for previous commit, since it does not include tox fixes.

Signed-off-by: Arnaud Morin <arnaud.morin@ovhcloud.com>
Change-Id: I821d846543f1dd55564358550fa074333f8b741b

.zuul.d/zuul.yaml

@@ -1,7 +1,7 @@
 - project:
     check:
       jobs:
-        - rally-tox-cover
+        #- rally-tox-cover
         - rally-tox-pep8
         - rally-tox-py36
         - rally-tox-py37
@@ -83,7 +83,7 @@
         #- rally-verify-tempest
     gate:
       jobs:
-        - rally-tox-cover
+        #- rally-tox-cover
         - rally-tox-pep8
         - rally-tox-py36
         - rally-tox-py37

tox.ini

@@ -1,6 +1,5 @@
 [tox]
 minversion = 3.1.1
-skipsdist = True
 ignore_basepython_conflict = true
 envlist = py36,py37,py38,pep8
 
@@ -13,7 +12,7 @@ setenv = VIRTUAL_ENV={envdir}
          LC_ALL=C
          PYTHONHASHSEED=0
          TOX_ENV_NAME={envname}
-whitelist_externals = find
+allowlist_externals = find
                       rm
                       make
 deps =
@@ -26,7 +25,14 @@ commands =
   python {toxinidir}/tests/ci/pytest_launcher.py tests/unit --posargs={posargs}
 distribute = false
 basepython = python3
-passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY REQUESTS_CA_BUNDLE
+passenv =
+  http_proxy
+  HTTP_PROXY
+  https_proxy
+  HTTPS_PROXY
+  no_proxy
+  NO_PROXY
+  REQUESTS_CA_BUNDLE
 
 [testenv:pep8]
 commands = flake8