draw_state: Fix Microsoft C++ assert

draw_state: Fix Microsoft C++ assert

The C++ runtime library was issuing an assert on the following line:
for (vector<CMD_NODE*>::iterator ii=pCB->pCmds.begin(); ii!=pCB->pCmds.end(); ++ii) {

It was complaining that the iterator ii was not compatible with the
pCmds.end(). Tracing down the assert, the C++ library did not like the
fact that we were accessing pCmds through a pointer (pCB). If we made a
local copy of the pCmds vector the assert went away.