Possible Issue: Repeated steps for key generation on Mac, Confusing for configuration

Walking through the steps [here](https://medalla.launchpad.ethereum.org/generate-keys) with this configuration:

```
1. How many validators would you like to run? 1
2. Current operating system? Mac (Mojave 10.14.4)
3. Install developer libraries? Already installed
4. Generate deposit keys using Ethereum Foundation tool? *Encountered issue here!*
```

When I run `./deposit.sh install`, it walks me through generating a keypair through mnemonic, asks me to write down the mnemonic, etc. However, when I run the next command on the line, `./deposit.sh --num_validators 1 --chain medalla`, it walks me through the *same* generation process.

It's confusing from a UX standpoint, because it seems like I'm running the whole process again (exact same instructions).

EDIT: It does seem to be an unnecessary duplication, creating two sets of validator keys.