Config utils improvement

Added a function to free resources allocated by config node tree.

Change-Id: I2ee8ae642899ec4501fa6e490c5be7efaa2d738e
diff --git a/libcutils/config_utils.c b/libcutils/config_utils.c
index 75fa6c6..fc5ca78 100644
--- a/libcutils/config_utils.c
+++ b/libcutils/config_utils.c
@@ -315,3 +315,15 @@
     data = load_file(fn, 0);
     config_load(root, data);
 }
+
+void config_free(cnode *root)
+{
+    cnode *cur = root->first_child;
+
+    while (cur) {
+        cnode *prev = cur;
+        config_free(cur);
+        cur = cur->next;
+        free(prev);
+    }
+}