Don't use install_command with tox

When tox py37 target is called, first it installs the dependencies
(listed in 'deps') in 'installdeps' phase, then it installs
tripleo-ansible with install_command in 'develop-inst' phase.
And installdeps phase would install the wrong setuptools not
constrained with uc[1] and hence the failure.

Also, adds setuptools to requirements.

[1] https://review.opendev.org/c/openstack/requirements/+/830960

Related-Bug: #1962232
Change-Id: I5b23a7649a4061dae3bc24a947022b027d95458e

requirements.txt

@@ -1,2 +1,3 @@
 pbr>=1.6
+setuptools>=57.5.0
 paunch>=5.1.0 # Apache-2.0

tox.ini

@@ -5,7 +5,6 @@ skipdist = True
 
 [testenv]
 usedevelop = True
-install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/train} {opts} {packages}
 passenv = *
 setenv =
   VIRTUAL_ENV={envdir}
@@ -20,7 +19,6 @@ setenv =
   ANSIBLE_RETRY_FILES_ENABLED=0
   ANSIBLE_STDOUT_CALLBACK=debug
   ANSIBLE_LOG_PATH={envlogdir}/ansible-execution.log
-  VIRTUAL_ENV={envdir}
   # pip: Avoid 2020-01-01 warnings: https://github.com/pypa/pip/issues/6207
   # paramiko CryptographyDeprecationWarning: https://github.com/ansible/ansible/issues/52598
   PYTHONWARNINGS=ignore:DEPRECATION::pip._internal.cli.base_command,ignore::UserWarning
@@ -29,8 +27,10 @@ setenv =
 
 sitepackages = True
 deps =
-   -r {toxinidir}/test-requirements.txt
-   -r {toxinidir}/ansible-requirements.txt
+   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/train}
+   -r{toxinidir}/requirements.txt
+   -r{toxinidir}/test-requirements.txt
+   -r{toxinidir}/ansible-requirements.txt
 commands = stestr run {posargs}
 whitelist_externals =
   bash
@@ -86,7 +86,8 @@ commands =
 [testenv:docs]
 basepython = python3
 deps =
-  -r {toxinidir}/doc/requirements.txt
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/train}
+  -r{toxinidir}/doc/requirements.txt
 commands=
     doc8 doc
     sphinx-build -a -E -W -d doc/build/doctrees -b html doc/source doc/build/html -T