(#7911) Allow managing local groups when duplicate names exist in a remote NSS database e.g. LDAP.

Some applications require local accounts and the useradd/groupadd commands currently used by the provider will not create a local account if they already exist remotely. The libuser commands luseradd/lgroupadd will allow a local name to duplicate a remote name. So these commands are used to force the local account creation. The libuser commands parse /etc/libuser.conf to determine which modules to use for creating users. Files must be the module used to get the desired local account managment. Because of this, it is necessary for Puppet to ship a libuser.conf file, which will only be used during a Puppet run, to ensure local account managment. The libuser.conf file used by the luseradd/lgroupadd commands can be overrideen by setting the environment variable LIBUSER_CONF. Which is what Puppet does to make sure its version of the configuration file is used