tox: Drop envdir

tox now always recreates an env although the env is shared using envdir
options.
~~~
$ tox -e genpolicy
genpolicy: recreate env because env type changed from
{'name': 'genconfig', 'type': 'VirtualEnvRunner'} to
{'name': 'genpolicy', 'type': 'VirtualEnvRunner'}
~~~

According to the maintainer of tox, this functionality is not intended
to be supported.
https://github.com/tox-dev/tox/issues/425#issuecomment-1011944293

There is a note not to remove the option for bandit integration job but
the note is no longer valid since the functionality itself no longer
works with recent tox.

Change-Id: I2ba52a9ecc5cc24dee98837e0513897cba2eb046

tox.ini

@@ -135,7 +135,6 @@ commands =
 [testenv:fast8]
 description =
   Run style checks on the changes made since HEAD~. For a full run including docs, use 'pep8'
-envdir = {toxworkdir}/shared
 extras =
 commands =
   bash tools/flake8wrap.sh -HEAD
@@ -151,7 +150,6 @@ commands =
   bash tools/check-cherry-picks.sh
 
 [testenv:api-samples]
-envdir = {toxworkdir}/functional
 setenv =
   {[testenv]setenv}
   GENERATE_SAMPLES=True
@@ -163,13 +161,11 @@ commands =
   stestr slowest
 
 [testenv:genconfig]
-envdir = {toxworkdir}/shared
 extras =
 commands =
   oslo-config-generator --config-file=etc/nova/nova-config-generator.conf
 
 [testenv:genpolicy]
-envdir = {toxworkdir}/shared
 extras =
 commands =
   oslopolicy-sample-generator --config-file=etc/nova/nova-policy-generator.conf
@@ -179,7 +175,6 @@ commands =
 # section once we rely on coverage 4.3+
 #
 # https://bitbucket.org/ned/coveragepy/issues/519/
-envdir = {toxworkdir}/shared
 setenv =
   {[testenv]setenv}
   PYTHON=coverage run --source nova --parallel-mode
@@ -193,7 +188,6 @@ commands =
   coverage report
 
 [testenv:debug]
-envdir = {toxworkdir}/shared
 extras =
 commands =
   oslo_debug_helper {posargs}
@@ -224,7 +218,6 @@ commands =
 [testenv:pdf-docs]
 description =
   Build PDF documentation.
-envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 extras =
 commands =
@@ -235,7 +228,6 @@ commands =
 [testenv:api-guide]
 description =
   Generate the API guide. Called from CI scripts to test and publish to docs.openstack.org.
-envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 extras =
 commands =
@@ -245,7 +237,6 @@ commands =
 [testenv:api-ref]
 description =
   Generate the API ref. Called from CI scripts to test and publish to docs.openstack.org.
-envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 extras =
 commands =
@@ -255,7 +246,6 @@ commands =
 [testenv:releasenotes]
 description =
   Generate release notes.
-envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 extras =
 commands =
@@ -265,7 +255,6 @@ commands =
 [testenv:all-docs]
 description =
   Build all documentation including API guides and refs.
-envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 extras =
 commands =
@@ -275,9 +264,6 @@ commands =
   {[testenv:releasenotes]commands}
 
 [testenv:bandit]
-# NOTE(browne): This is required for the integration test job of the bandit
-# project. Please do not remove.
-envdir = {toxworkdir}/shared
 extras =
 commands = bandit -r nova -x tests -n 5 -ll