Consider to log a package list for pip3

When we run devstack with USE_PYTHON3=True, a package may be
installed by pip2 or pip3 depending on package classifier.
So we should try to log a package list by pip2 and pip3.

Change-Id: I06e2559e852f0dabbbbb8f6c0dc081cedb745b60

functions.sh

@@ -874,9 +874,14 @@ function cleanup_host {
 
     sudo iptables-save > $WORKSPACE/iptables.txt
     df -h > $WORKSPACE/df.txt
-    pip freeze > $WORKSPACE/pip-freeze.txt
-    sudo mv $WORKSPACE/iptables.txt $WORKSPACE/df.txt \
-        $WORKSPACE/pip-freeze.txt $BASE/logs/
+    sudo mv $WORKSPACE/iptables.txt $WORKSPACE/df.txt $BASE/logs/
+
+    for py_ver in 2 3; do
+        if [[ `which python${py_ver}` ]]; then
+            python${py_ver} -m pip freeze > $WORKSPACE/pip${py_ver}-freeze.txt
+            sudo mv $WORKSPACE/pip${py_ver}-freeze.txt $BASE/logs/
+        fi
+    done
 
     if [ `command -v dpkg` ]; then
         dpkg -l> $WORKSPACE/dpkg-l.txt