Make `env` and `plugins` commands local again
    
    During thin client refactoring, LocalOrRemote class implementation of `run`
    method was overriden by default Command implementation during instantiation of
    client plugins from schema. This caused these commands to always forward this
    request to IPA master.
    
    This patch restores the original behavior: unless `--server` option was
    specified, the commands will always print out local config.
    
    https://fedorahosted.org/freeipa/ticket/6490
    
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>