Fix secure MapR cluster creation error in streamsets branch

[kirtiv1]

In the streamsets branch, while creating secure MapR cluster, it is producing following error:

2018-01-03 11:01:53 PM clusterdock.topology_mapr.start INFO     Creating sdc user directory in MapR-FS ...
mkdir: failure to login: Unable to obtain MapR credentials
chown: failure to login: Unable to obtain MapR credentials