Fix "sudo: sorry, you must have a tty to run sudo"

On many systems the requiretty sudoers option is turned on by default.
With "requiretty" option the sudo ensures the user have real tty access.

Just several "su" variant has an option for skipping the new session creation step.

Only one session can posses a tty, so after a "su -c" the sudo will not
work.

We will use sudo instead of su, when we create the stack account.

This change adds new variable the STACK_USER for
 service username.

Change-Id: I1b3fbd903686884e74a5a22d82c0c0890e1be03c
diff --git a/lib/ceilometer b/lib/ceilometer
index 749e785..0fae397 100644
--- a/lib/ceilometer
+++ b/lib/ceilometer
@@ -9,6 +9,7 @@
 # - OS_AUTH_URL for auth in api
 # - DEST set to the destination directory
 # - SERVICE_PASSWORD, SERVICE_TENANT_NAME for auth in api
+# - STACK_USER service user
 
 # stack.sh
 # ---------
@@ -94,7 +95,7 @@
 function init_ceilometer() {
     # Create cache dir
     sudo mkdir -p $CEILOMETER_AUTH_CACHE_DIR
-    sudo chown `whoami` $CEILOMETER_AUTH_CACHE_DIR
+    sudo chown $STACK_USER $CEILOMETER_AUTH_CACHE_DIR
     rm -f $CEILOMETER_AUTH_CACHE_DIR/*
 }