fix(*): set etcd keys safely in /bin/boot

Each etcd configuration key should be set-if-unset. Previously,
we were setting all of these defaults if one directory existed,
but it's safer to set each one individually if it is unset.

Author: carmstrong

bin/boot

@@ -24,13 +24,16 @@ done
 # wait until etcd has discarded potentially stale values
 sleep $(($ETCD_TTL+1))
 
-# seed initial service configuration if necessary
-if ! etcdctl --no-sync -C $ETCD ls $ETCD_PATH >/dev/null 2>&1; then
-	etcdctl --no-sync -C $ETCD set $ETCD_PATH/protocol ${DEIS_PROTOCOL:-http} >/dev/null
-	etcdctl --no-sync -C $ETCD set $ETCD_PATH/secretKey ${DEIS_SECRET_KEY:-`openssl rand -base64 64 | tr -d '\n'`} >/dev/null
-	etcdctl --no-sync -C $ETCD set $ETCD_PATH/builderKey ${DEIS_BUILDER_KEY:-`openssl rand -base64 64 | tr -d '\n'`} >/dev/null
-	etcdctl --no-sync -C $ETCD set $ETCD_PATH/registrationEnabled 1 >/dev/null
-fi
+function etcd_safe_set {
+  if ! etcdctl --no-sync -C $ETCD get $ETCD_PATH/$1 >/dev/null 2>&1; then
+    etcdctl --no-sync -C $ETCD set $ETCD_PATH/$1 $2 >/dev/null
+  fi
+}
+
+etcd_safe_set protocol ${DEIS_PROTOCOL:-http}
+etcd_safe_set secretKey ${DEIS_SECRET_KEY:-`openssl rand -base64 64 | tr -d '\n'`}
+etcd_safe_set builderKey ${DEIS_BUILDER_KEY:-`openssl rand -base64 64 | tr -d '\n'`}
+etcd_safe_set registrationEnabled 1
 
 # wait for confd to run once and install initial templates
 until confd -onetime -node $ETCD -config-file /app/confd.toml 2>/dev/null; do