virtualisation.qemu.program: Remove

This option is defined in qemu-vm.nix, but that module is not always
imported.

http://hydra.nixos.org/build/44817443
(cherry picked from commit 03c55005dfd6fbcd5cf8e00128a3bb6336b3bc0f)

nixos/lib/testing.nix

@@ -29,7 +29,7 @@ rec {
         cp ${./test-driver/Logger.pm} $libDir/Logger.pm
 
         wrapProgram $out/bin/nixos-test-driver \
-          --prefix PATH : "${lib.makeBinPath [ qemu_kvm vde2 netpbm coreutils ]}" \
+          --prefix PATH : "${lib.makeBinPath [ qemu_test vde2 netpbm coreutils ]}" \
           --prefix PERL5LIB : "${with perlPackages; lib.makePerlPath [ TermReadLineGnu XMLWriter IOTty FileSlurp ]}:$out/lib/perl5/site_perl"
       '';
   };