Fix possible dead lock in CircularByteBuffer test

The CircularByteBuffer function waitForData runs a loop as long as the
condition "isEmpty() && running" is true.
If the buffer is empty before the next check is done the loop will never
end (as no more data is inserted in the buffer).
Merge pull request #5 from maggu2810/CircularByteBufferTest-fix

Fix possible dead lock in CircularByteBuffer test