try different options

tests/data/slapd-chain1.conf

@@ -29,6 +29,11 @@ argsfile    ./testrun/slapd.1.args
 #monitormod#modulepath ../servers/slapd/back-monitor/
 #monitormod#moduleload back_monitor.la
 
+#
+# uses the chain overlay as global;
+# no chain-URI is configured, so the URI is parsed out of the referral
+overlay		chain
+
 #######################################################################
 # database definitions
 #######################################################################
@@ -47,6 +52,4 @@ rootpw		secret
 index		objectClass	eq
 index		cn,sn,uid	pres,eq,sub
 
-overlay		chain
-
 #monitor#database monitor

tests/data/slapd-chain2.conf

@@ -47,6 +47,9 @@ rootpw		secret
 index		objectClass	eq
 index		cn,sn,uid	pres,eq,sub
 
+#
+# uses the chain overlay as database specific;
+# the chain-URI is configured, so only that URI is chained
 overlay		chain
 chain-uri	@URI1@