Revert "s4:tls_tstream: allow mode of SSL keyfile to be 0400, not only 0600"

Revert "s4:tls_tstream: allow mode of SSL keyfile to be 0400, not only 0600"

This reverts commit 05c1fe50556e2330e23b7efb38e653428b9bdadf.

This was discussed here:
https://bugzilla.samba.org/show_bug.cgi?id=10392#c11

This generated warnings like:
invalid permissions on file
'/memdisk/metze/W/b138235/samba/bin/ab/promoted_dc/private/tls/key.pem': has
0600 should be 0400'.

I think we need a better way. Maybe file_check_permissions()
should get allow_perms and deny_perms. And we would call it
with allow_perms = 0400 and deny_perms = 0177. And bits in none
of them are ignored.

For now we revert this and wait for a better fix.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Fri Mar 28 12:37:17 CET 2014 on sn-devel-104