LU-7988 hsm: don't use a ptlrpc_thread struct for the cdt

LU-7988 hsm: don't use a ptlrpc_thread struct for the cdt

Since only the waitq and the event flag from the ptlrpc_thread
structure are used, declare these directly and do not use the
ptlrpc_thread structure at all.

Test-Parameters: trivial testlist=sanity-hsm
Signed-off-by: frank zago <fzago@cray.com>
Change-Id: Iba63ac70ad381f7e40976ac423594eae46c5249b
Reviewed-on: https://review.whamcloud.com/22761
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Henri Doreau <henri.doreau@cea.fr>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>