Enable execution of heat-manage db_sync

This patch is aiming to correct a fault in puppet-heat that was not
executing the heat-manage db_sync that was making this module in the
end not fully working.

At this stage there are no tests to support this change but I am
willing to add those in a later commit.

This patch it's been rebased according to this change: https://review.openstack.org/46227

This new patchset include a patch from Sebastien Badia and should
make all the tests green with Change id: I2aa8fc070e5f5ee18040200e4a5b4f6161550280

Change-Id: Ib7731ab429ea92947f52bcf015facc8864466586
Merge "Enable execution of heat-manage db_sync"