Client: Make plugin helper override directory mode u=rwx,go=
Even though it currently is not used, a local administrator might use setuid (or setcap) executables as plugin helpers. Thus, the plugin helper override directory (/etc/mandos/plugin-helpers) must be secured, just as the plugin override directory (/etc/mandos/plugins.d) is.
* Makefile (install-client-nokey): Install plugin-helper directory as mode u=rwx. * debian/mandos-client.lintian-overrides: Do not warn about permissions on plugin helper directory. * debian/mandos-client.postinst (configure): Fix permissions on plugin helper local override directory (/etc/mandos/plugin-helpers), but only if not listed by "dpkg-statoverride".