tests/db_test: close the database when test is finished

Change-Id: I96fedf9181e89e4d68815b04f494a9c2ecc0e057
diff --git a/tests/db/db_test.c b/tests/db/db_test.c
index cc299bf..91b32ea 100644
--- a/tests/db/db_test.c
+++ b/tests/db/db_test.c
@@ -979,6 +979,7 @@
 	test_subscr_sqn();
 
 	printf("Done\n");
+	db_close(dbc);
 	return 0;
 }