Should mounting holes have solder bumps?
Assuming that the mounting holes are plated and connected to ground, the presence of solder bumps will help in two ways -


The connection to ground can still be maintained even if the screws are not fully tightened.
If somebody over-tightens the screws, the solder bumps will take damage first (they flatten up) before damaging the annular ring on the mounting hole.


The second point will be valid for both plated and non-plated mounting holes.