rgmanager: OCF_NOT_INSTALLED is OK if we stop when stopped
    
    Scripts often live in file systems which are mounted by
    rgmanager.  This patch makes rgmanager ignore the
    OCF_NOT_INSTALLED error returned from the script agent if
    we attempt to stop when a start failed.
    
    Furthermore, don't mark the resource as failed if a start
    failure occurs due to the program not existing.
    
    The combination of these create the ability for a missing
    script to move to a node where the script exists, or be
    placed in to the stopped state.
    
    Resolves: rhbz#768146
    
    Signed-off-by: Lon Hohberger <lhh@redhat.com>
    Reviewed-by: Adam Drew <adrew@redhat.com>
    Tested-by: Adam Drew <adrew@redhat.com>