Ceph » CephFS

Add new tests in ceph/qa to test the new recover_session=clean mount option in kcephfs, and set them up to run in teuthology. To start:

1. mount fs using kcephfs and recover_session=clean
2. open some file descriptors and do activity with them
3. blacklist client
4. perform new operations and wait for it to "clean" the state

At a minimum, I think we'd want to test these operations on fds that were open before blacklisting:

1. reading from an fd open before blacklist
2. writing to an fd that was open before blacklist
3. set filelock on fd, and attempt to read/write to it after being blacklisted (should return -EIO)
4. write data before the blacklisting and attempt to fsync afterward (should work, I guess?)