Adobeconnect default start/end times not being correctly calculated

Description of the issue
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The default end time for an adobe connect activity could default to a time before the start time, which means that it will throw a validation error if you try to add the activity with the default values supplied.

Steps to reproduce
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1. Go to: Site Administration > Location > Location Settings and set "Default timezone" to something other than "Server's local time" (e.g. UTC+3)
2. Add an Adobe Connect activity to a course site, and see that the default end time is not two hours after the start time, as expected (e.g. it is 1 hour before)

Expected Behaviour
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Default end time should be default start time + 2 hours

Resolution
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Patch attached

Patch and github repo
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Links to be provided in comments section once I get a tracker number for this issue