Teleporting an entity with relative position isn't working correctly.

Description: When you have a command block teleport an entity using relative position it will teleport the entity to the command block and not the correct relative position.

Reproduction steps.
1. Put the following commands into two command blocks that are 1 or 2 blocks apart.
summon MinecartRideable ~ ~1 ~

{CustomName:F1,NoGravity:1}

tp @e[name=F1] ~ ~2 ~

2. Summon the Minecart with the command block and make note of the location
3. Activate the command block to teleport the Minecart and make note of where it teleported to.
4. Keep activating the teleport command block to see if the position changes.

Expected results: The minecart should have teleported 2 blocks up from it's current position.

Actual Results: The minecart teleport to be above the second command block and would not teleport higher if you keep activating the teleport command block.