Permit use of sudo-ldap instead of sudo package

If the sudo-ldap package is providing the sudo command instead of the plain
sudo package, accept that instead of breaking the system and requiring direct
root login intervention to fix things.

Change-Id: I45d7e4617bd59e72b4f0bf2e91750a6830e2a010
diff --git a/tools/create-stack-user.sh b/tools/create-stack-user.sh
index c0b7ac7..919cacb 100755
--- a/tools/create-stack-user.sh
+++ b/tools/create-stack-user.sh
@@ -32,7 +32,7 @@
 source $TOP_DIR/stackrc
 
 # Give the non-root user the ability to run as **root** via ``sudo``
-is_package_installed sudo || install_package sudo
+is_package_installed sudo || is_package_installed sudo-ldap || install_package sudo
 
 [[ -z "$STACK_USER" ]] && die "STACK_USER is not set. Exiting."