sssd: style nitpick - don't use pkgs parameter

pkgs/os-specific/linux/sssd/default.nix

@@ -1,13 +1,14 @@
-{ stdenv, fetchurl, fetchpatch, pkgs, glibc, augeas, dnsutils, c-ares, curl,
+{ stdenv, fetchurl, fetchpatch, glibc, augeas, dnsutils, c-ares, curl,
   cyrus_sasl, ding-libs, libnl, libunistring, nss, samba, nfs-utils, doxygen,
   python, python3, pam, popt, talloc, tdb, tevent, pkgconfig, ldb, openldap,
   pcre, kerberos, cifs-utils, glib, keyutils, dbus, fakeroot, libxslt, libxml2,
   libuuid, ldap, systemd, nspr, check, cmocka, uid_wrapper,
-  nss_wrapper, ncurses, Po4a, http-parser, jansson
-  , withSudo ? false }:
+  nss_wrapper, ncurses, Po4a, http-parser, jansson,
+  docbook_xsl, docbook_xml_dtd_44,
+  withSudo ? false }:
 
 let
-  docbookFiles = "${pkgs.docbook_xsl}/share/xml/docbook-xsl/catalog.xml:${pkgs.docbook_xml_dtd_44}/xml/dtd/docbook/catalog.xml";
+  docbookFiles = "${docbook_xsl}/share/xml/docbook-xsl/catalog.xml:${docbook_xml_dtd_44}/xml/dtd/docbook/catalog.xml";
 in
 stdenv.mkDerivation rec {
   name = "sssd-${version}";
@@ -32,7 +33,7 @@ stdenv.mkDerivation rec {
   preConfigure = ''
     export SGML_CATALOG_FILES="${docbookFiles}"
     export PYTHONPATH=${ldap}/lib/python2.7/site-packages
-    export PATH=$PATH:${pkgs.openldap}/libexec
+    export PATH=$PATH:${openldap}/libexec
 
     configureFlagsArray=(
       --prefix=$out