selftest: Be explicit about which testenvs use ntvfs

selftest: Be explicit about which testenvs use ntvfs

If a testenv didn't specify any other provision arguments, then it
defaulted to using the NTVFS file server.

This patch makes it explicit, so we just pass through "--use-ntvfs" as
extra provision args in the cases we want.

(Whether all these testenvs really need to use NTVFS or not is another
question, but at least now it's easy to see which testenvs use it).

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13676

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>