PG-1468 Fix issue with intolerably slow recovery

When we did a recovery, even if tde_heap was not used, 98% of the time
was spent in pg_tde_get_key_from_file() due to our SMGR missing the
shortcicruit from mdcreate() which skips running if the fork already
is open.

The issue was made worse by us not caching negative SMGR key lookups but
that is the subject of another commit.

contrib/pg_tde/src/smgr/pg_tde_smgr.c

@@ -195,7 +195,10 @@ tde_mdcreate(RelFileLocator relold, SMgrRelation reln, ForkNumber forknum, bool
 {
 	TDESMgrRelation tdereln = (TDESMgrRelation) reln;
 	InternalKey *key;
-	TdeCreateEvent *event = GetCurrentTdeCreateEvent();
+
+	/* Copied from mdcreate() in md.c */
+	if (isRedo && tdereln->md_num_open_segs[forknum] > 0)
+		return;
 
 	/*
 	 * Make sure that even if a statement failed, and an event trigger end
@@ -215,6 +218,8 @@ tde_mdcreate(RelFileLocator relold, SMgrRelation reln, ForkNumber forknum, bool
 
 	if (forknum == MAIN_FORKNUM || forknum == INIT_FORKNUM)
 	{
+		TdeCreateEvent *event = GetCurrentTdeCreateEvent();
+
 		/*
 		 * Only create keys when creating the main/init fork. Other forks can
 		 * be created later, even during tde creation events. We definitely do