commit d453a4aa implemented that for the crash
recovery case (not marking the node down and then not promoting the mirror). It
seems that we should do that for the usual "starting up" case also(i.e.
CAC_STARTUP), besides for the existing "in recovery mode" case (i.e.
CAC_RECOVERY).

We've seen that fts promotes the "starting up" primary during isolation2
testing due to 'pg_ctl restart'. In this patch we check recovery progress for
both CAC_STARTUP an CAC_RECOVERY during fts probe and thus can avoid this.
Reviewed-by: NAshwin Agrawal <aagrawal@pivotal.io>

cherry-picked from d71b3afd

On master the commit message was eliminated by mistake. Added back on gpdb6.