start_timestamp/end_timestamp and start/end is not unified

[Liusheng]

In 'ceilometer alarm-history', we can use start_timestamp/end_timestamp in query field;

In 'ceilometer resource-list', we can use start_timestamp/end_timestamp in query field;

In 'ceilometer sample-list', we can use start/end in query field;

In 'ceilometer statistics', we can use start/end in query field;

We should make these unified.

additionally, the 'timestamp' in query field has the same function

[gordon chung (chungg)]

switching to ceilometerclient... please change back if this is incorrect.

[Openstack Gerrit (openstack-gerrit)]

Fix proposed to branch: master
Review: https://review.openstack.org/90636

[gordon chung (chungg)]

resolved by https://review.openstack.org/#/c/128856/9