Description of problem:

If you create a Sync Plan with a future start date, using the API or hammer but not the web UI, and if the value in the seconds field is not zero, it will skip one interval when creating the first sync date and time.

Version-Release number of selected component (if applicable):
[root@sat-6-5-qa-rhel7 ~]# rpm -q foreman
foreman-1.20.1.31-1.el7sat.noarch
[root@sat-6-5-qa-rhel7 ~]# rpm -q tfm-rubygem-foreman-tasks
tfm-rubygem-foreman-tasks-0.14.4.5-1.el7sat.noarch

How reproducible:

See examples in BZ#1685724

Actual results:

Sync Plans created by API calls have "next_sync" time and date set to one interval later than the creation time and date.

Expected results:

Sync Plan should be created with "next_sync" time and date within one interval

Additional info:

https://github.com/SatelliteQE/robottelo/pull/6825