r312: let ntvfs posix backend return NT_STATUS_ACCESS_DENIED in the connect hook

r312: let ntvfs posix backend return NT_STATUS_ACCESS_DENIED in the connect hook
and print out an error message to the debug log which say:
use 'cifs' or 'simple' as ntvfs handler
this also warns about 'root' fileaccess in the 'simple' module

the 'default' ntvfs handler is now registered by the posix backend

metze
(This used to be commit 84b3589daa60cfdd2c868d9468192b0a6e1eebae)