Replication Strategy creation errors are lost in try/catch

I was initially executing a bad cassandra-stress command and was getting this error:

Unable to create stress keyspace: Error constructing replication strategy class

with the following command:

cassandra-stress -o insert --replication-strategy NetworkTopologyStrategy --strategy-properties dc1:1,dc2:1 --replication-factor 1

After digging in the code, I noticed that the error displayed was not the one thrown by the replication strategy code and that the try/catch block could be improved. Basically, the Constructor.newInstance can throw an InvocationTargetException, which provide a better error report.

I think this improvement can also be done in 2.1 (not tested yet). If my attached patch is acceptable, I will test and provide the right version for 2.1 and trunk.

With the patch, I can see the proper error when executing my bad command:

Unable to create stress keyspace: replication_factor is an option for SimpleStrategy, not NetworkTopologyStrategy