libvirt: correct localstatedir (#109415)

It was supposed to be '/var' rather than '/var/lib'. This fixes an issue
where some tools don't connect to the right socket (because they were
connecting to '$localstatedir/run/libvirt...' instead of
'$runstatedir/libvirt...').

Also change runstatedir to just be '/run' since it avoids a log line
complaining about that.

pkgs/development/libraries/libvirt/default.nix

···
   in [
     "--sysconfdir=/var/lib"
     "-Dinstall_prefix=${placeholder "out"}"
-    "-Dlocalstatedir=/var/lib"
-    "-Drunstatedir=/var/run"
+    "-Dlocalstatedir=/var"
+    "-Drunstatedir=/run"
     "-Dlibpcap=enabled"
     "-Ddriver_qemu=enabled"
     "-Ddriver_vmware=enabled"