Try this:

geth --ipcpath eth-test-chain/geth.ipc --datadir eth-test-chain --networkid 15

it worked for me. I guess the --rpc option is interfering with the IPC interface.

Or if you need to get access to console, from another terminal issue:

geth --ipcpath eth-test-chain/geth.ipc --datadir eth-test-chain --networkid 15 console

I believe you can just kill the contract. Please read to the end before attempting it.

Steps to take

1. From https://www.myetherwallet.com/#contracts, enter 0xaD24B48f33746e68BDCDC2E7F5857eE0EeEc2EFB as the contract address, and then paste the ABI. You can copy the whole thing from here: https://etherscan.io/address/0xaD24B48f33746e68BDCDC2E7F5857eE0EeEc2EFB#code. (Click the "copy" button to the right of "Contract ABI.")
2. Then pick the function "kill," and enter the address you want to send the ether to (so make sure it's an address you have the private key for) as a value for the _to field. Be really careful about this step.
3. Next, unlock the account using the Keystore/JSON file + password or whatever form you have the private key in.
4. Finally, click "WRITE" at the bottom of the page, and then "Generate Transaction." From there, you can either copy the raw transaction (to submit it later) or go ahead and submit it to the network.

Additional notes

For added security, consider downloading an offline version of MyEtherWallet and doing this all locally (and ideally disconnected from the network). You can download an offline version via a link in the footer on https://www.myetherwallet.com. In that last step above, you can copy down the raw transaction, and then go back online (or transfer it to another computer) to submit it. Etherscan has a nice tool for pasting in a raw transaction and sending it out to the network.

Use ETH Gas Station to figure out a good gas price. You can set the gas price on MEW via a dropdown in the upper right corner of the page. At the time I write this, 5 or 6 gwei seems good.

EDIT

You can do the same thing with the execute function. Pass a _to address that will receive the funds, and a _value of how much ether to send (in wei). _data can actually be anything, but I believe 0x0 is the right value to just send an empty bytes.