Make the patch ideompotent

geocoder/admin0/patches/20160622_countries_synonym_congo.sql

@@ -1,3 +1,9 @@
 -- Patch 0.0.1 data version -20160622
-
+DO $$
-INSERT INTO admin0_synonyms (name, rank, adm0_a3) VALUES ('Republic of the Congo', 10, 'COG');
+    DECLARE exiting INTEGER;
+BEGIN
+    SELECT count(*) FROM admin0_synonyms WHERE name = 'Republic of the Congo' AND adm0_a3 = 'COG' and rank = 10 INTO exiting;
+    IF exiting = 0 THEN
+        INSERT INTO admin0_synonyms (name, rank, adm0_a3) VALUES ('Republic of the Congo', 10, 'COG');
+    END IF;
+END$$;