kube-up: move sha1sum-file into common

Also hash the tar files in AWS kube-up

cluster/common.sh

@@ -441,3 +441,11 @@ function build-runtime-config() {
       fi
   fi
 }
+
+function sha1sum-file() {
+  if which shasum >/dev/null 2>&1; then
+    shasum -a1 "$1" | awk '{ print $1 }'
+  else
+    sha1sum "$1" | awk '{ print $1 }'
+  fi
+}