Set shell options for reliability.

Tweak a few other small things in our shell scripts.

cluster/saltbase/install.sh

@@ -21,7 +21,8 @@ set -o errexit
 set -o nounset
 set -o pipefail
 
-readonly SALT_ROOT=$(dirname "${BASH_SOURCE}")
+SALT_ROOT=$(dirname "${BASH_SOURCE}")
+readonly SALT_ROOT
 
 readonly SERVER_BIN_TAR=${1-}
 if [[ -z "$SERVER_BIN_TAR" ]]; then
@@ -31,7 +32,7 @@ fi
 
 # Create a temp dir for untaring
 KUBE_TEMP=$(mktemp -d -t kubernetes.XXXXXX)
-trap "rm -rf ${KUBE_TEMP}" EXIT
+trap 'rm -rf "${KUBE_TEMP}"' EXIT
 
 # This file is meant to run on the master.  It will install the salt configs
 # into the appropriate place on the master.