[StarCluster] Start retry

[David Erickson]

 >>> Validating cluster template settings...
 >>> Cluster template settings are valid
 >>> Starting cluster...
 >>> Launching a 1-node cluster...
 >>> Creating security group @sc-Optimizer...
 >>> Creating placement group @sc-Optimizer...
!!! ERROR - InsufficientInstanceCapacity: Insufficient capacity.

It would be great if there was an option to tell starcluster to continue 
retrying until it is able to get the instance(s) needed, with possible 
options to fail after trying X number of times or after Y real time has 
elapsed.

Thanks!
David