Create the stack users ~./cache early

This creates the users ~/.cache directory with proper permissions
prior to running devstack/grenade, avoiding potential permission
issues if a later pip installation is run with sudo but without -H.

Change-Id: I033fd8a28ed593da343315b6fc5a7658ca8c4e31
Related-bug: #1405626

functions.sh

@@ -443,6 +443,11 @@ function setup_host {
     sudo chown root:root $TEMPFILE
     sudo mv $TEMPFILE /etc/sudoers.d/50_stack_sh
 
+    # Create user's ~/.cache directory with proper permissions, ensuring later
+    # 'sudo pip install's do not create it owned by root.
+    sudo mkdir -p $BASE/new/.cache
+    sudo chown -R stack:stack $BASE/new/.cache
+
     # Create a tempest user for tempest to run as, so that we can
     # revoke sudo permissions from that user when appropriate.
     # NOTE(sdague): we should try to get the state dump to be a