Update tox.ini files from release-tools gold copy

All OpenStack Charms now contain identical tox.ini files,
not to be modified or made unique within each charm repo.

This is to ensure consistency across charm repos in tox
target naming, approach and purpose, also giving the
charm dev and test experience additional consistency.

Change-Id: I56da049ddeb3f6d7b51afa4e88a7e1fce9a2cf9c

tox.ini

@@ -1,3 +1,6 @@
+# Classic charm: ./tox.ini
+# This file is managed centrally by release-tools and should not be modified
+# within individual charm repos.
 [tox]
 envlist = pep8,py27
 skipsdist = True
@@ -6,10 +9,11 @@ skipsdist = True
 setenv = VIRTUAL_ENV={envdir}
          PYTHONHASHSEED=0
          AMULET_SETUP_TIMEOUT=2700
-passenv = HOME TERM AMULET_HTTP_PROXY AMULET_OS_VIP
 install_command =
   pip install --allow-unverified python-apt {opts} {packages}
 commands = ostestr {posargs}
+whitelist_externals = juju
+passenv = HOME TERM AMULET_*
 
 [testenv:py27]
 basepython = python2.7
@@ -20,7 +24,7 @@ deps = -r{toxinidir}/requirements.txt
 basepython = python2.7
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = flake8 {posargs} --exclude */charmhelpers hooks unit_tests tests actions
+commands = flake8 {posargs} hooks unit_tests tests actions
            charm-proof
 
 [testenv:venv]
@@ -72,4 +76,4 @@ commands =
 
 [flake8]
 ignore = E402,E226
-exclude = hooks/charmhelpers
+exclude = */charmhelpers