VFS: default: let vfswrap_is_offline() take conn, not handle

VFS: default: let vfswrap_is_offline() take conn, not handle

vfswrap_is_offline() has been converted to a "helper" function some time ago, it
had been a VFS interface function before. To make this change more obvious let
it take a struct connection_struct instead of a struct vfs_handle_struct which
is the canonical first parameter to VFS functions.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14293

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>