fix(store): don't output secretKey and accessKey

In 33fb20e, the removal of the
output redirect for `radosgw-admin user create` means that the
accessKey and secretKey are output in the journal when the user
is created. As these are secrets, they shouldn't ever be printed.

This commit redirects the output of this command to /dev/null.

Author: carmstrong

store/gateway/bin/boot

@@ -83,7 +83,7 @@ else
 fi
 
 if ! radosgw-admin user info --uid=deis >/dev/null 2>&1 ; then
-  radosgw-admin user create --uid=deis --display-name="Deis"
+  radosgw-admin user create --uid=deis --display-name="Deis" >/dev/null
 fi
 
 radosgw-admin user info --uid=deis >/etc/ceph/user.json