Fixing flaky crash after 17.5 merge

The 17.5 release includes a bugfix for the smgrcode: previously
if smgropen failed, smgrclose wasn't called.

In our case we tried to retrieve the key before calling mdopen in
smgropen, which meant that the open call failed before the data
initialization in mdopen, which sometimes caused mdclose to crash.

The fix is simple: as mdopen only zero initializes some data, we
call it before trying to retrieve the principal key. This way the
failure happens after every data structure is set up properly.

Author: dutow

contrib/pg_tde/src/smgr/pg_tde_smgr.c

@@ -250,7 +250,11 @@ static void
 tde_mdopen(SMgrRelation reln)
 {
 	TDESMgrRelation tdereln = (TDESMgrRelation) reln;
-	InternalKey *key = tde_smgr_get_key(&reln->smgr_rlocator);
+	InternalKey *key;
+
+	mdopen(reln);
+
+	key = tde_smgr_get_key(&reln->smgr_rlocator);
 
 	if (key)
 	{
@@ -261,7 +265,6 @@ tde_mdopen(SMgrRelation reln)
 	{
 		tdereln->encrypted_relation = false;
 	}
-	mdopen(reln);
 }
 
 static const struct f_smgr tde_smgr = {