entity_metadata.go: Fix incorrectly enconding of packedEffects

[IvanCraft623]

The implementation has the following problems:

• Does not include ambient indicator
• Only the first two effects are correctly packed
  • This is caused because for some reason you are multiplying the shift 7 by the index. (wtf??).
    • On the first iteration nothing happened because it gave a bit shift of 0, as it is the first iteration it does not matter if there is bit shift or not.
    • On the second iteration 7 * 1, the shift is correct, Ok
    • From the third iteration on, the shifts are incorrect.

I almost had a stroke with the go syntax

[TwistedAsylumMC]

Thanks!