You want to disable the dashed rubber band line

You want to disable the dashed lined rubber band displayed when in edit mode (moving, copying, etc) a line.

 

The rubber band cannot be turned off, but prior to AutoCAD 2015 the color could be changed by going into Options > Display > Colors and changing "Dynamic dimension lines." Changes made to the rubber band in AutoCAD 2015-2016 stopped this from working.

For more information on the rubberband/rubber band:

http://knowledge.autodesk.com/article/How-to-disable-or-change-the-color-of-the-rubber-band-in-AutoCAD

This has been reported to Autodesk and may change in the next release.