Move the posix pending close functionality down into the VFS layer.

Move the posix pending close functionality down into the VFS layer.

This hides the pending close fds from the outside. Call order
of SMB_VFS_CLOSE is reversed. Originally, it was:

fd_close -> fd_close_posix -> SMB_VFS_CLOSE -> close

And now it is:

fd_close -> SMB_VFS_CLOSE -> fd_close_posix -> close

This is in preparation of removing the fd parameter
from the SMB_VFS_CLOSE function. But it is also the right
place for the pending close calls anyways.

Michael