LU-5538 mdc: Report D_CHANGELOG messages as D_HSM.

LU-5538 mdc: Report D_CHANGELOG messages as D_HSM.

Removed the D_CHANGELOG pseudo-debug flag that wasn't actually defined
as a usable one. Report the D_CHANGELOG messages as D_HSM ones instead
since this is the primary user of these messages.

Signed-off-by: Henri Doreau <henri.doreau@cea.fr>
Change-Id: I4d82b16935d053e1b7e43512a1b9368f4b0316b5
Reviewed-on: http://review.whamcloud.com/11558
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>