storage_conf: plug a leak on OOM error path

* src/conf/storage_conf.c (virStoragePoolSourceListNewSource):
Free just-allocated "source" upon VIR_REALLOC_N failure.

src/conf/storage_conf.c

 /*
  * storage_conf.c: config handling for storage driver
  *
- * Copyright (C) 2006-2009 Red Hat, Inc.
+ * Copyright (C) 2006-2010 Red Hat, Inc.
  * Copyright (C) 2006-2008 Daniel P. Berrange
  *
  * This library is free software; you can redistribute it and/or
@@ -1695,6 +1695,7 @@ virStoragePoolSourceListNewSource(virConnectPtr conn,
     }
 
     if (VIR_REALLOC_N(list->sources, list->nsources+1) < 0) {
+        VIR_FREE(source);
         virReportOOMError(conn);
         return NULL;
     }