Fix $LOGDIR owner to be stack.stack

I have seen this failure in the gate a few times:

[ERROR] /opt/stack/devstack/functions-common:2334 Neutron did not start
/opt/stack/devstack/functions-common: line 310:
  /opt/stack/logs/error.log: Permission denied

So whatever was trying to be written to error.log never
happened. Change to be like other directories in this
file and make the $LOGDIR owner stack.stack.

Change-Id: I673011aba10c8d03234100503ccc5876e75baff2

stack.sh

@@ -349,7 +349,9 @@ fi
 
 # Destination path for devstack logs
 if [[ -n ${LOGDIR:-} ]]; then
-    mkdir -p $LOGDIR
+    sudo mkdir -p $LOGDIR
+    safe_chown -R $STACK_USER $LOGDIR
+    safe_chmod 0755 $LOGDIR
 fi
 
 # Destination path for service data