->pid in filesystem code

Yes the cifs vfs code was using current->pid in multiple places and in about five of the places the meaning
really was process id, and thus presumably better to change this to current->tgid. I have made the change
from pid to tgid for those places in the bk tree for the cifs vfs (http://cifs.bkbits.net/linux-2.5cifs) and will try them out.

The locking tests needed to be rerun anyway.