opentsdb: fixup sandboxed builds

http://hydra.nixos.org/build/46688690
/cc maintainer @rickynils.

pkgs/tools/misc/opentsdb/default.nix

···
   buildInputs = [ autoconf automake curl jdk makeWrapper nettools python git ];
 
   preConfigure = ''
+    patchShebangs ./build-aux/
     ./bootstrap
   '';