use Oozie delegation token, if provided

The oozie shell-action script which invokes "slider create" must dynamically create a token.conf file, as follows:

echo "<configuration><property><name>mapreduce.job.credentials.binary</name><value>${HADOOP_TOKEN_FILE_LOCATION}</value></property></configuration>" > token.conf

Then, the script invokes "slider create -conf token.conf" with the included changes.