Minor fixes to scripts.

bin/copy-all-and-measure

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 ./destroy-target
 

bin/create-and-measure

@@ -3,9 +3,9 @@
 ./destroy-test
 zfs create -o compression=lz4 tank/test
 SCRIPT_DIR="$(pwd)"
-pushd /tank/test
+pushd /tank/test || exit
 cat "$SCRIPT_DIR/$1"
 time "$SCRIPT_DIR/$1"
-popd
+popd || exit
 zfs snapshot tank/test@final
 ./display-usage