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

Change-Id: I2f82337223a936a3ed89f43e249a06e86d0f141b

tox.ini

@@ -29,7 +29,6 @@ commands =
   stestr run {posargs}
 
 [testenv:pep8]
-envdir = {toxworkdir}/shared
 commands = flake8
            {toxinidir}/tools/check_unit_test_structure.sh
            {toxinidir}/tools/coding-checks.sh --pylint '{posargs}'
@@ -65,7 +64,6 @@ commands =
   stestr run {posargs}
 
 [testenv:cover]
-envdir = {toxworkdir}/shared
 setenv =
   {[testenv]setenv}
   PYTHON=coverage run --source ovn_octavia_provider --parallel-mode
@@ -77,7 +75,6 @@ commands =
   coverage report --fail-under=92 --skip-covered
 
 [testenv:docs]
-envdir = {toxworkdir}/docs
 deps =
   -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/doc/requirements.txt
@@ -85,7 +82,6 @@ deps =
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:pdf-docs]
-envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 allowlist_externals =
   make
@@ -94,11 +90,9 @@ commands =
   make -C doc/build/pdf
 
 [testenv:debug]
-envdir = {toxworkdir}/shared
 commands = oslo_debug_helper -t ovn_octavia_provider/tests {posargs}
 
 [testenv:releasenotes]
-envdir = {toxworkdir}/docs
 deps = -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
@@ -132,7 +126,6 @@ extension =
 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
@@ -155,7 +148,6 @@ commands =
     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
 deps = -r{toxinidir}/test-requirements.txt
 commands = bandit -r ovn_octavia_provider -x tests -n5