Blockchains are designed not to forget, so you cannot "teardown" a stream per se.
In most cases, if your purpose is testing, you should create a new blockchain for each test. This is quite simple to automate using multichain-util (and its command line parameters) and multichaind with the initprivkey and shortoutput runtime parameters (if you need them).
You can delete a blockchain by stopping the node and removing the ~/.multichain/[chain-name] directory.