Add coverage-log(-post) macros to reduce duplication

Change-Id: I9d54b93ade444880bb79ed799b6b6ea95833be44
Reviewed-on: https://review.openstack.org/19578
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins