gflags isn't initialized when REGISTER_MODULE_INITIALIZER is invoked,
we couldn't initialize vmodule_list properly. Modified to call
VLOG2Initializer in the first call of InitVLOG3__.


git-svn-id: https://google-glog.googlecode.com/svn/trunk@8 eb4d4688-79bd-11dd-afb4-1d65580434c0