Yes, over contributing to your 401(k) is considered an "Excess Salary Deferral".

No, you should not create a mock Form 1099-R. 

You can report the refund of the excess contributions to your 401K on Line 7 of your 2017 Tax Return without a Form 1099-R by following these steps: 

• Click on the "Federal Taxes" Tab
• Click on the "Wages & Income" Tab
• Click on "I'll choose what I work on"
• Scroll down to "Less Common Income"
• Select "Miscellaneous Income" and click Start or Update
• Select "Other income not already reported on a Form W-2 or Form 1099" and click on Start
  
• Answer the Question "Did you receive any other wages?  Yes
  
• Click through the questions until you get to "Any Other Earned Income"
• Answer Yes to "Did you earn any other wages?
• Indicate "Other" as Source of Other Earned Income and click Continue
• For the description enter "2017 Excess 401K Deferrals" and click on Done

You will receive a 2018 Form 1099-R in 2019 with a code P in box 7 which you can ignore if the excess deferral is reported as suggested above.  However, the earnings will be reported on a separate 2018 Form 1099-R with a Code "8" in Box 7 that should be reported on your 2018 tax return.