fix another race. vscsi_cmd checked if the adapter was running at

fix another race. vscsi_cmd checked if the adapter was running at
the start and queued the command for processing by userland later.
the adapter could stop running between the check and the queue.
this merges the state and queue mutexes and combines the check and
queue ops in vscsi_cmd into the same critical section.

tweaked by and ok matthew@