GRMLBASE/39-modprobe: avoid usage of /lib/modprobe.d/50-nfs.conf

The /lib/modprobe.d/50-nfs.conf file as shipped with
nfs-kernel-server >=1:2.6.2-1 causes plenty of problems,
like:

* https://bugs.debian.org/1024082 ("nfs-kernel-server:
  /lib/modprobe.d/50-nfs.conf causing problems with sysctl from busybox
  and with kmod")
* https://bugs.debian.org/1022172 ("/lib/modprobe.d/50-nfs.conf causes
  initramfs-tools to stop including sunrpc module for nfs")

So instead, let's ensure we don't ship the upstream file.

Closes: grml/grml#193

etc/grml/fai/config/scripts/GRMLBASE/39-modprobe

@@ -17,5 +17,10 @@ find $target/etc/modprobe.d -maxdepth 1 -type f ! -name \*\.conf -exec mv {} {}.
 # Install all present modprobe.d configuration files
 fcopy -v -i -r /etc/modprobe.d
 
+if [ -f "${target}/lib/modprobe.d/50-nfs.conf" ] ; then  # nfs-kernel-server >=1:2.6.2-1
+  echo "Clearing /lib/modprobe.d/50-nfs.conf to avoid automatic kmod/busybox issues"
+  echo '# this file was generated by grml-live script GRMLBASE/39-modprobe' > "${target}/lib/modprobe.d/50-nfs.conf"
+fi
+
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