Disable tempest tox venv recreation in OFFLINE mode

Setting OFFLINE=True in local.conf should enable stack.sh to run multiple
times without an internet connection. This was broken for some cases
when recreation of tox venv for tempest was forced in lib/tempest.

This change makes recreation of tox venv enabled only when OFFLINE mode is
disabled.

Change-Id: I2bf6caf60038a3690378eead905b35e9175ac356
Closes-Bug: #1550537

Author: skazi0

lib/tempest

@@ -322,7 +322,9 @@ function configure_tempest {
     local tmp_cfg_file
     tmp_cfg_file=$(mktemp)
     cd $TEMPEST_DIR
-    tox -revenv --notest
+    if [[ "$OFFLINE" != "True" ]]; then
+        tox -revenv --notest
+    fi
     # NOTE(mtreinish): Respect constraints on tempest verify-config venv
     tox -evenv -- pip install -c $REQUIREMENTS_DIR/upper-constraints.txt -r requirements.txt
     tox -evenv -- tempest verify-config -uro $tmp_cfg_file