Add integration test for crypto service rekeys

An integration test exercising the use of encrypted and unencrypted data, using multiple keys, and rekeying should be implemented. The order of events to get this in one test should look something like:

1. Start Accumulo without encryption
1. Create a table
1. Write to the table
1. Read the data
1. Stop Accumulo (in Uno, this would be 'uno stop Accumulo --no-deps')
1. Enable encryption and specify a key file
1. Restart Accumulo
1. Write to the existing table
1. Read the data (which will now be a mixture of encrypted and unencrypted data)
1. Stop Accumulo
1. Specify a new key file (leaving the old one)
1. Start Accumulo
1. Write to the existing table
1. Read the data (which should now be a mixture of encrypted data from two keys and unencrypted data)
1. Run a compaction
1. Check the RFile tails to make sure only the 2nd key is used and that all RFiles are encrypted

I suspect the Accumulo restarts are necessary to reset the configurations, but there might be a cleaner way to do that.