Classes introduction:

TestCase:
    base class for (AioTestCase,...)
    It contains: 
                data: store the test result
                void printStatus(): print the test result

AioCase: public TestCase
    base class for all asynchronous test case
    It contains:
                run() to execute a test case
                virtual void start_io(...) to start an asynchronous io

AioWriteCase: public AioCase
                aio_write_completion() to deal result after an asynchronous write io ends
                implement start_io() 

AioReadCase: public AioCase
                aio_read_completion() to deal result after an asynchronous read io ends
                implement start_io() 
Bench:
    It stores base info of the ceph cluster, pool name, image name, rados object, ioctx object, rbd object...
    It contains:
        int registerTestCase(...): register test case
        run(): to run all test case

RbdBench:
   main program
   It read from rbd.testCase.in, and parse the parameter of test case and filter rule.
   finally run all test case one by one