Fix URI to work with either back-ldap or back-meta

tests/data/slapd-proxycache.conf

@@ -35,7 +35,7 @@ argsfile    ./testrun/slapd.2.args
 database	ldap
 suffix          "o=University of Michigan,c=US"
 rootdn          "o=University of Michigan,c=US"
-uri		ldap://127.0.0.1:9011
+uri		ldap://127.0.0.1:9011/o=University%20of%20Michigan%2cc=US
 
 overlay proxycache
 proxycache	@BACKEND@ 100 2 @ENTRY_LIMIT@ @CACHETTL@