Activate virtual environment

Enable virtualenv after installation. Without it, python packages from
system location will be used. So if bindep is not installed in system
packages the failure will be as

~/tripleo-validations/scripts/..//scripts/bindep-install: line 37: bindep: command not found

This patch activates virtualenv after creation on previous step in
accordance rather than before pytest.

Change-Id: I3725bf64bead30b02f10eb9a68d220c4e422b531

scripts/run-local-test

@@ -47,6 +47,9 @@ sudo touch /etc/ci/mirror_info.sh
 # Create a virtual env
 "${PYTHON_EXEC}" -m virtualenv --system-site-packages "${HOME}/test-python"
 
+# Activate a virtual env
+PS1="[\u@\h \W]\$" source "${HOME}/test-python/bin/activate"
+
 # Run bindep
 "${HOME}/test-python/bin/pip" install "pip>=19.1.1" setuptools bindep --upgrade
 "${PROJECT_DIR}/scripts/bindep-install"
@@ -61,7 +64,6 @@ fi
                               -r "${PROJECT_DIR}/molecule-requirements.txt"
 
 # Run local test
-PS1="[\u@\h \W]\$" source "${HOME}/test-python/bin/activate"
 source "${PROJECT_DIR}/ansible-test-env.rc"
 export ANSIBLE_ROLES_PATH="${ANSIBLE_ROLES_PATH}:${HOME}/zuul-jobs/roles"
 ansible-playbook -i "${PROJECT_DIR}/tests/hosts.ini" \