Set cg_file_data_ to null when initialization failed

Cannot really do calls if initialization failed.
Also fix LOG usage.

But: 124774415
Test: Build
Change-Id: Ifd7db90cfee51ba5830e1d4db8f8d19b5bc9feba
diff --git a/libprocessgroup/cgroup_map.h b/libprocessgroup/cgroup_map.h
index ba2caf7..1c355cd 100644
--- a/libprocessgroup/cgroup_map.h
+++ b/libprocessgroup/cgroup_map.h
@@ -92,5 +92,5 @@
     ~CgroupMap();
 
     bool LoadRcFile();
-    void Print();
+    void Print() const;
 };