Remove DEFAULT_STACK_USER, just use STACK_USER

STACK_USER needs to be set for more than just stack.sh, there
was no real distinction for using DEFAULT_STACK_USER instead
of just setting STACK_USER directly in stackrc and allowing it
to be overridden in localrc.

Change-Id: I9e8d70db29bb421f1ce3dbf40a5ad299cc7ea785
diff --git a/stack.sh b/stack.sh
index 005d88e..e50cc49 100755
--- a/stack.sh
+++ b/stack.sh
@@ -160,7 +160,6 @@
 # sudo privileges and runs as that user.
 
 if [[ $EUID -eq 0 ]]; then
-    STACK_USER=$DEFAULT_STACK_USER
     ROOTSLEEP=${ROOTSLEEP:-10}
     echo "You are running this script as root."
     echo "In $ROOTSLEEP seconds, we will create a user '$STACK_USER' and run as that user"
@@ -196,7 +195,6 @@
     fi
     exit 1
 else
-    STACK_USER=`whoami`
     # We're not **root**, make sure ``sudo`` is available
     is_package_installed sudo || die "Sudo is required.  Re-run stack.sh as root ONE TIME ONLY to set up sudo."
 
@@ -1291,7 +1289,7 @@
 CURRENT_RUN_TIME=$(date "+$TIMESTAMP_FORMAT")
 echo "# $CURRENT_RUN_TIME" >$TOP_DIR/.stackenv
 for i in BASE_SQL_CONN ENABLED_SERVICES HOST_IP LOGFILE \
-  SERVICE_HOST SERVICE_PROTOCOL TLS_IP; do
+  SERVICE_HOST SERVICE_PROTOCOL STACK_USER TLS_IP; do
     echo $i=${!i} >>$TOP_DIR/.stackenv
 done