tox: Remove unnecessary configuration

These were either unnecessary or overrode default configuration.

Change-Id: Ie17998dc564f06e9133c8412c24bc041b1e9a603

tox.ini

@@ -45,7 +45,6 @@ commands =
   env TEST_OSPROFILER=1 stestr run --combine --no-discover 'nova.tests.unit.test_profiler'
 
 [testenv:pep8]
-basepython = python2.7
 deps = {[testenv]deps}
 commands =
   bash tools/flake8wrap.sh {posargs}
@@ -59,7 +58,6 @@ commands =
 # only runs flake8 on the changes made since
 # HEAD-1. For a full flake8 run including checking
 # docs, just use pep8.
-basepython = python2.7
 commands =
   bash tools/flake8wrap.sh -HEAD
 
@@ -67,7 +65,6 @@ commands =
 # TODO(melwitt): This can be removed when functional tests are gating with
 # python 3.x
 basepython = python2.7
-usedevelop = True
 setenv = {[testenv]setenv}
 commands =
   {[testenv]commands}
@@ -86,7 +83,6 @@ commands =
 # with python 3.5
 [testenv:functional-py35]
 basepython = python3.5
-usedevelop = True
 setenv = {[testenv]setenv}
 commands =
   {[testenv]commands}
@@ -101,7 +97,6 @@ commands =
   stestr --test-path=./nova/tests/functional --group_regex=nova\.tests\.functional\.api\.openstack\.placement\.test_placement_api(?:\.|_)([^_]+) run {posargs}
 
 [testenv:api-samples]
-usedevelop = True
 setenv =
   {[testenv]setenv}
   GENERATE_SAMPLES=True