Fix openrc source when invoked with bash nounset option

This change fixes the check for the --no-credentials argument to handle
the case where no argument is present and nounset is active, i.e.:
  set -o nounset

In this case we default $1 to "" via ${1:-}

Test Plan:

Pass:
- Build and source the /etc/platform/openrc file with and without
  arguments. Test with and without the nounset option.

Closes-Bug: 2051549

Change-Id: Iab7f21d26751b024bf58c41b16aac79daa351abf
Signed-off-by: Kyle MacLeod <kyle.macleod@windriver.com>

puppet-manifests/src/modules/platform/templates/openrc.admin.erb

@@ -1,7 +1,7 @@
 # Usage: source this file with parameter "--no_credentials" to avoid exporting
 # user and password. Also, PS1 variable is not set.
 
-if [[ $1 == "--no_credentials" ]]; then
+if [[ "${1:-}" == "--no_credentials" ]]; then
     no_credentials=true
 else
     no_credentials=false
@@ -12,7 +12,7 @@ unset OS_SERVICE_TOKEN
 export OS_ENDPOINT_TYPE=internalURL
 export CINDER_ENDPOINT_TYPE=internalURL
 
-if [[ "$no_credentials" == false ]]; then
+if [[ "${no_credentials}" == false ]]; then
     export OS_USERNAME=<%= @admin_username %>
     export OS_PASSWORD=`TERM=linux <%= @keyring_file %> 2>/dev/null`
 fi
@@ -26,7 +26,7 @@ export OS_IDENTITY_API_VERSION=<%= @identity_api_version %>
 export OS_REGION_NAME=<%= @identity_region %>
 export OS_INTERFACE=internal
 
-if [[ "$no_credentials" == false ]]; then
+if [[ "${no_credentials}" == false ]]; then
     if [ ! -z "${OS_PASSWORD}" ]; then
         export PS1='[\u@\h \W(keystone_$OS_USERNAME)]\$ '
     else