There is an easily changed setting to prevent these requests for your password whenever you need to walk away from your computer for a while.
First follow this path:
Dash --> System Settings --> Personal --> Brightness & Lock
Then take the following two steps:
- Set the 'Lock' setting to 'Off'
- Uncheck the setting 'Require my Password when waking from suspend'
I have tested this successfully with both Trusty Tahr 14.04 LTS and Xenial Xerus 16.04 LTS. Below is a screenshot from Xenial Xerus to illustrate the technique:
Obviously this shows the setting activated, you need to remove the tick (the check in the check box) by clicking on it.
Note: Keep in mind that this disables a security feature of Ubuntu, possibly not relevant in your case but relevant to many other Ubuntu users. This feature is designed to protect your computer from unauthorized use by others while you are away from your computer for a period of time...