s4-server: move the creation of the IPC$ share into ntvfs

s4-server: move the creation of the IPC$ share into ntvfs

the IPC$ share is only used by the ntvfs backends, and doesn't need to
be created on every load of smb.conf. This fixes a problem with
testparm showing the ipc$ share when it isn't defined in smb.conf.

This also removes the admin$ share, which really shouldn't be on by
default. The admin$ share is used for remote software installation,
and normally exposes the c:\windows directory on a windows
server. That makes no sense on Samba. If for some reason a admin$
share is needed, then the admin can create one as usual. Exposing /tmp
via admin$ by default seems like a bad idea.

Pair-Programmed-With: Andrew Bartlett <abartlet@samba.org>