LU-4516 mdc: missing lexxx_to_cpu in mdc_read_entry

LU-4516 mdc: missing lexxx_to_cpu in mdc_read_entry

A few missing lexx_to_cpu on some accesses to lu_dirpage/lu_dirent
in MDC.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: I50d9d8916004ef460bd7a49376306e2d6bda2b99
Reviewed-on: http://review.whamcloud.com/9331
Tested-by: Jenkins
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>