LU-2781 mdt: initialize mti_spec.sp_rm_entry

LU-2781 mdt: initialize mti_spec.sp_rm_entry

Prevent previous assignments to mti_spec.sp_rm_entry from affecting
the current operation by setting it to 0 in mdt_thread_info_init().

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Iee41cd0e48718338d83b62e0610bd5d23d80dc47
Reviewed-on: http://review.whamcloud.com/5327
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>