SmsServerPropertiesResource removes password when unchanged.

Bug description

SmsServerPropertiesResource removes password when unchanged.

How to reproduce the issue

1. run ldapsearch to check "org.forgerock.services.cts.store.password" exists :

 $./ldapsearch -p 51389 -D "cn=Directory Manager" -w cangetin -b ou=services,dc=openam,dc=forgerock,dc=org "objectclass=*" | grep "serverconfig=org.forgerock.services.cts.store.password" 

2. login to admin console
3. click [Configure] -> [Server Defaults] -> [Advanced] tab
4. scroll down and change "org.forgerock.services.cts.store.max.connections" to 11.
5. click [Save Changes]
6. run ldapsearch again to check "org.forgerock.services.cts.store.password" still exists :

 $./ldapsearch -p 51389 -D "cn=Directory Manager" -w cangetin -b ou=services,dc=openam,dc=forgerock,dc=org "objectclass=*" | grep "serverconfig=org.forgerock.services.cts.store.password" 

NOTE: if you've already configured session failover and CTS store per instance, then you might see more than one "org.forgerock.services.cts.store.password" so you need to check the value under server-default

Expected behaviour

SmsServerPropertiesResource shouldn't remove org.forgerock.services.cts.store.password when the value is null.

Current behaviour

SmsServerPropertiesResource marks org.forgerock.services.cts.store.password as unwanted and remove from server default

Work around

Always specify org.forgerock.services.cts.store.password when making a change on server default advanced tab.

Code analysis

Fix to OPENAM-11850 has made SmsServerPropertiesResource to remove "org.forgerock.services.cts.store.password" from "newValues" lists. This tricked removeUnusedAdvancedAttributes() method that "org.forgerock.services.cts.store.password" is no longer needed and therefore need to be removed.

The fix would be to skip removing attributes that are listed in "PASSWORD_ATTRIBUTES". The downside is that this way, users wouldn't be able to remove "PASSWORD_ATTRIBUTES" from XUI Advanced tab.

    private void removeUnusedAdvancedAttributes(SSOToken token, Set<String> newAttributeNames, String serverName)
            throws SSOException, SMSException, InternalServerErrorException {

        ServiceConfig serviceConfig = getServerConfigs(token).getSubConfig(serverName);
        List<String> attributesToRemove = getAdvancedTabAttributeNames(serviceConfig);
        attributesToRemove.removeAll(newAttributeNames);
        attributesToRemove.removeAll(PASSWORD_ATTRIBUTES);  <--- FIX
        try {
            serverConfiguration.removeServerConfiguration(token, serverName, attributesToRemove);
        } catch (IOException e) {
            throw new InternalServerErrorException("Failed to remove server configuration", e);
        }
    }