Unify installer context to be 'installer'
    
    'install' was being used in some places.
    
    The context can be used to limit what configuration is
    used for a given request so having consistency is
    valuable.
    
    This affected the force_schema_updates value in LDAPClient
    which looks for api.env.context in ('installer', 'updates')
    
    Related: https://pagure.io/freeipa/issue/8798
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Rafael Guterres Jeffman <rjeffman@redhat.com>