history: updated ksm_shared_memory_percent to mb

Droped ksm_shared_memory_percent column from
host_samples_history table
and added ksm_shared_memory_mb instead.

Updated etl of ksm_shared_memory_percent,
max_ksm_shared_memory_percent columns in
host_samples_history, hourly and
daily tables to ksm_shared_memory_mb and
max_ksm_shared_memory_percent.

Change-Id: Ic965021913baa1a3a95deda5ab2cad206638cbbb
Bug-Url: https://bugzilla.redhat.com/1076902
Signed-off-by: Shirly Radco <sradco@redhat.com>